Best Vape Mods and Box Mods in 2021: Everything You Need to Know
Vape mods combine powerful, high-capacity battery sections with compatible 510-threaded tanks, either MTL or sub-ohm tanks, as well as RBAs and RDTAs.
Standard mods use either single, dual or even triple 18650 cells. Vape mods also feature highly advanced chipsets that offer vapers a wide range of vaping styles from variable wattage, temperature control and even bypass mode (direct voltage output) along with several safety features.
Thanush PoulsenUpdated: July 7, 2021
VooPoo Drag 2
Great choice for beginners
The VooPoo Drag 3 is the latest version of the brand’s legendary Drag mod that features a new, GENE.FAN chipset and still uses two 1865...
The best box mods and vape mods contain advanced chipsets that can precisely read and monitor the atomizer resistance as well as control power and or temperature.
Vape mods are larger than vape pens as well as most tube mods. They have an array of additional features: variable voltage, wattage, and temperature setting.
Vapers who start with e-cigs and vape pens eventually look for something more powerful and customizable. While some vape pens offer a degree of customization, none can produce much power. This leaves vapers a bit starved for something more. For the ultimate power, customization, and vapor production, vape mods are the way to go. On this page, we are reviewing the best available vape mods.
Here’s a list of the very best regulated box mods. We focussed on several areas in our ranking structure. The four top-rated vape mods on the list are perfect for real-world, everyday vaping and offer exceptional long-term value. Our top four best box mods all come as complete kits including battery.
As you move further into the list, you will find specialty box mods of all types. Since we chose only the top performers, you won’t notice a lot of cons, although we’ll mention any weaknesses that any particular mod has.
It’s important to understand what mAh actually means when buying a box mod. The mAh can give a good indication of how long the cell will last. For instance, a 1 Amp mod would get roughly 2 and a half hours of vaping with this size battery.
The VooPoo Drag 3 is the latest version of the brand’s legendary Drag mod that features a new, GENE.FAN chipset and still uses two 18650s batteries. The Drag 3 departs from its predecessor’s design style by combining a sturdy, zinc alloy base with leather wrapping that gives it a soft touch. The Drag 3 features a new 1.8” TFT screen for easier navigation, as well as a super-fast firing time of less than a 0.001 seconds. The Drag 3 enables several vaping outputs like Smart Mode and Super Mode that gives users an extra boost whenever vaping in wattage mode. The Drag 3 is also the platform VooPoo is using to launch their TPP-based pod atomizer with a new coil design.
Reasons to Get This Device:
If you used previous versions of the Drag
The updated GENE.FAN chipset with various, new vaping outputs
A new, exterior design that matches zinc alloy and leather
Bright, eye-catching TFT display for easy operation
New TPP Pod Tank and matching TPP coils
Accessories and Kit Contents
As the VooPoo Drag 3 comes with a new tank/pod hybrid it comes with several accessories to support the TPP Pod tank, which has a glass dome that fits over a stainless steel base with dual airflow vents. Here’s what else comes in the kit:
Perfect VW and TC modes with instant 0.001s firing speed
Powerful 1-230 Wattage capacity
Improved protection features
The SMOK Morph 2 is a dual 18650 box mod that has several different build elements like touch-screen, die-cast zinc, and stainless steel.
These different materials make the mod, waterproof, shockproof and dustproof. The device also features a front-facing, 0.96 9″ HD touchscreen and side-firing button to manage its many vaping features.
The firing button though is traditional press-button mods. The Morph carries the IQ-S chipset inside that allows the device to reach a maximum power output of 219W. Its vaping modes include variable wattage, temperature control, and bypass or curve modes.
Vapers can also use a power curve mode on the Morph mod. The device has a spring-loaded, gold-plated 510 connection up top. The mod has a USB port right under the screen, and it can take firmware updates, also through the USB port. At the moment Morph is new box mod, so the update is still on-time.
Slimmer, more portable build than the regular Drag
Also updated with the new GENE.FAN chipset
Reasons to Get This Device:
Versatile battery options (single 18650 or 21700)
Slimmer, more portable build than the regular Drag
Also updated with the new GENE.FAN chipset
Combines zinc alloy build with soft-touch leather
Compatible with RBAs and other rebuildable atomizers
The VooPoo Drag X Plus is a unique version of the Drag series of mods as it uses only a single cell, but still features the powerful GENE.FAN chipset that can propel the device to output a respectable 100W. The Drag X Plus has a slimmer, more manageable build than the regular, dual-18650 version of the Drag but it still retains several high-performance features. The device has several vaping outputs like Smart and Super mode, as well as a bypass and wattage mode. The Drag X Plus also features an RBA mode that users can pair with their favorite rebuildable atomizer or they can attach any 510-threaded sub-ohm tank for regular sub-ohm vaping.
Accessories and Kit Contents
VooPoo has also chosen the Drag X Plus to premier their new TPP tank/pod hybrid that features a unique glass dome and stainless steel base and can hold up to 5.5ml of e-liquid. Along with the TPP tank, there are a few coil options and other accessories:
Soft-touch rubberized coating for more comfortable grip
Zinc-alloy chassis is sturdy and lightweight
Standard vaping outputs (VW, TC) along with unique Vaporesso offerings (Power mode, Pulse mode)
The Vaporesso Gen S 220W is a new mod from Vaporesso that boasts colorful exterior paint options and advanced vaping performance. The Vaporesso Gen S is a dual-18650 device that takes its batteries in a side-panel battery bay that is kept in place with a magnetic connection. The side-mounted control panel features a 0.91” OLED screen that lets users choose from one of the AXON chip’s several outputs. Users can vape in standard wattage (up to 220W) or temperature control mod or choose from one of the more innovative options like Power mode (that conserves battery power) or Pulse mode (that maintains temperature throughout temperature control mode).
Accessories and Kit Contents:
The Vaporesso Gen S comes paired with the fantastic SKRR-S sub-ohm tank with two coil options included. The rest of the kit includes the following:
The Vandy Vape Jackaroo is the newest device from Vandy Vape with the Vandy chipset included but this time in a nearly-indestructible outer surface. Borrowing from GeekVape, Vandy Vape opted to cover the Jackaroo in a mixture of soft-gel rubber over its internal magnesium-aluminum chassis. The Jackaroo is a dual-18650 device that can reach a mid-range power output of up to178W, but it also boasts several other high-performance vaping outputs like temperature control and bypass mode. The Vandy Vape Jackaroo also has the distinction of being Bluetooth compatible, which gives users the ability to download compatible apps like Find My Mod.
Accessories and Kit Contents
At the moment, the Jackaroo is only available as a stand-alone mod. It has a semi-centered 510-connection on top and it measures 30mm across so it has ample room to accommodate even large tanks. Here’s the full content list:
Build quality is great and the rubber coating is a nice touch
Good power mode performance and wattage and 2A charging is accurately rated
Handles atomizers of up to 26mm well and without overhang
Menu is easy to use and is nicely laid out
The 2.4-inch screen is excellent and intuitive
Flavor production is outstanding and vapor production is phenomenal
The 2.4-inch is prone to scratches
Not possible to get the full wattage in TC mode
Battery door is pretty weak and is a bit hard to close
The GeekVape Aegis X boasts a lot of impressive features including a 220-watt rating, a 2.4-inch OLED color screen, an IP67 certification for dust and water resistance, and updates AS 2.0 chipset.
With a frame made of zinc alloy, a carbon steel battery door cover, an advanced LSR injection molding technology, and an ergonomic soft-grip, it is solidly, sturdily, and nicely built. Thanks to Aegis X’s AS 2.0 chipset, it has a really quick response time, a really accurate temperature control, and an all-new balanced battery charging capability. This vape mod has a resistance range of 0.05 to 3 ohms. So it can be a good vape mod for salt nic if apply above ohm coil.
You may also choose from three different wallpapers for its 2.4-inch screen. There are also a lot of settings that you can play with, including power/wattage, TC-TCR, VPC, and bypass mode.
Single-cell configuration gives it a slight, slim profile
Ergonomic, four-button control panel
Perfect for RBAs and sub-ohm tanks
The Lost Vape Quest Grus does not feature the quintessential DNA chipset, but this device has enough to stand on its own merits. The Quest Grus is a single-cell device that gives it a slimmer, more lightweight profile. The Grus takes several battery types, which can support either 21700, 20700, or 18650 batteries. The Quest Grus features standard vaping outputs like wattage control and temperature control that users can control via the 0.91” TFT control panel. The controls feature a separate selector button for more straightforward navigation.
Accessories and Kit Contents:
As it is a Lost Vape device, the Quest Grus comes as a stand-alone mod. But it features a standard 510-connection up top and it measures close to 31mm in width, which means it can take several tank sizes, even outsized rebuildable tanks, and attys. Here’s the rest of the kit:
IP67-rated waterproof, shock proof and dust resistant
Three-button control panel for easy navigation
Very fast firing response time
Low power output for a 18650 device
The Vaporesso FORZ TX80 is a single 18650 device that comes as a stand-alone mod, but comes with several advanced features. The device features the Axon 2.0 chipset that lets the device reach a high power output of 80W. The chipset also enables you to engage in several vape modes from the embedded 0.69” OLED. The control panel features a standard two-button configuration but it is made easier with the addition of a separate mode button for easy selection. The FORZ has a standard 510-connection on top of its zinc-alloy construction that makes it compatible with many different types of tanks and atomizers.
The VooPoo Argus GT160W box mod is a dual-18650 device that features the updated GENE chipset called the GENE.TT. The new chipset offers a wide power output range of 5-160W and a full temperature control suite that lets users vape with stainless steel, nickel and titanium coils. The device also comes equipped with a well-lit OLED for easy access to the vape’s internal features, which pairs with a three-button control panel. The unit has a bottom battery door and uses a Micro USB port for charging and installing firmware upgrades.
Regulated device to use with your rebuildable atomizers
Device with a full complement of vaping outputs (VW, TC)
An elegant-looking device with a colorful screen
The Sigelei 213 FOG 200W vape mod is a dual-18650 device that has a clean, minimalist design but comes equipped with a full-color 0.96” TFT screen for easy navigation. The FOG device also comes with the new IFV60 chipset that has a good selection of new vaping outputs including variable wattage, temperature control and an auto-smart curve function. The device takes two 18650 cells in its bottom battery bay door.
The vaping industry is full of vape mods that will get the job done. While some mods are hard hitters, others are lacking in their power output. Our summary of the top vape mods shows you the best mods this industry has to offer in 2021. Read on to learn more about how the best box mods and vape mods compare against the competition.
Best Box Mod of 2021
1. VooPoo Drag 2
Best Powerful Vape
2. GeekVape Aegis X 200 Watt Box Mod
Best Vape Mod Starter Kit
3. VooPoo Drag X Pod Mod Starter Kit
Best Box Mod with a screen
4. Vaporesso Gen S 220W
Best Indestructible Vape Mod
5. VANDY VAPE JACKAROO DUAL 188W BOX MOD
Best Chip-set Mod
6. LOST VAPE QUEST GRUS
Best High Wattage Vape Mod
7. Smok Morph 2 Vape Mod 230W
Best Small Vape Mod
8. Vaporesso FORZ TX80
Best Vape Mod for Clouds
9. Voopoo Argus GT160W
Best Price-Quality Vape Mod
10. Sigelei 213 FOG 200W Vape Mod
Vape Mods 101
Old school regulated box mods came in two forms: variable voltage and variable wattage. Both types are usually confused as the same, but there are differences. Before explaining the differences between the two, it’s important to understand how watts (or power), volts, current (or amps), and resistances (or ohms) interact.
There are formulas to determine each variable – known as Ohm’s Law – and they are:
Voltage (V) = Current (I) x Resistance (R)
Power (P) = Voltage (V) x Current (I)
While you can calculate manually for each, there are Ohm’s law calculators you can use online to make things easier for you. That being said, determining your sweet spot means knowing how many watts your preferred vape is. If your perfect vape is achieved by using a 2.2-ohm atomizer at 4.2 volts, the power you’re getting is equal to 8 watts.
When using a variable voltage device with a 2.2-ohm atomizer, simply adjust the voltage to 4.2 volts to achieve your sweet spot. To achieve the same 8 watts with a 1.4-ohm atomizer, the voltage needs to be adjusted down to 3.3 volts.
Things are simpler for variable wattage. Using the above example, if your sweet spot is at 8 watts, you simply adjust the wattage of the device to 8 watts and the mod will adjust voltage accordingly. It doesn’t matter if you use a 2.5 ohm or a 0.5-ohm atomizer. Once wattage has been set, you’ll get your perfect vape every time. Based on these facts, variable wattage devices are true “set it and forget it” vapes.
Regulated Box Mods Vs. Mech Mods
Box vape mods are now more often preferred over mechanical mods. Many variable wattage mods can match the power outputs of other, more capable, mechanical mods that are on the market today. This preference over mechanical mods is because box mods are easier to use and maintain and are built with various safety features, such as short circuit protection, reverse battery protection, thermal protection, and automatic cutoffs, which prevent accidental fires inside the pocket or purse.
Even though box mods are safer than mechanical mods, they still need to be handled with care. All the reports of exploding mods are either because they were mechanical mods with no circuitry or there was damage to the cell due to mishandling.
Now, if you looked at our vape mod reviews above, you may have noticed that we mentioned several of them offer a “bypass” mode. Bypass mode will make a box mod work like a mech mod. Drippers will have an option to use the best box mods as a mech if they so wish. For most vapers, we recommend taking advantage of the precision control of today’s top-rated vape mods.
Box Mod Batteries
There are several types of batteries used in box mods. The various sizes are 18650, the most common by far, 20600, 20700, or 21700. The most common vape batteries you will see sold in stores are:
Lithium IMR or Li-Mn
Protected ICR Li-Ion
There is also another – LiPo batteries – but these are used as internal batteries. These are not safe chemistry, and protection depends on the circuitry of the mod. One might hear this name thrown about in vaping circles, but since these are not used as removable batteries, this type will not be discussed in-depth.
Lithium IMR and IMR/Hybrid batteries are safe chemistry, and these are recommended for use with mods. While Protected ICR Li-Ion batteries can still be found, these are not recommended and are considered obsolete.
Both types of IMR batteries are “high drain”, and while also called “unprotected,” they are also “safe chemistry” meaning they will not explode or light up under stress. Instead, they vent gas. These make them the most popular types of batteries vapers use for their mods. However, Lithium IMR types have a lesser capacity compared to ICR batteries. However, IMRs work best when the maximum load current is required.
For the curious, a short article on how lithium-ion batteries work can be read here.
The IMR/Hybrid batteries, on the other hand, have the same safe chemistry make up as Lithium IMRs but with more capacity. It is the newest type and the one most recommended by users. It renders obsolete both the ICR Protected and Lithium IMR batteries in one fell swoop. Some e-cig manufacturers (like MigVapor) sell special e-cig batteries that are ready to be connected to the vape tank of your choice.
What Vape Mod Is Right for You?
When picking the best vape mod, it all boils down to three categories: Experience, Budget, and Goals.
Most vape mods on this page are well-suited for vapers at any level of experience. Some of the best vape mods have very advanced features, are very powerful, and are best suited to experienced vapers. If you are a complete beginner, we recommend something with as fewer settings as possible, like, for example, Mig Vapor Neo.
The price of owning a vape mod is not only how much you pay for it, but also for how long it will last. You also have to consider the extra expense of batteries and a charger. As the most durable mod and the best bang for your buck, we recommend to check our “Cheap Vape Mods” page.
Are you looking for customizability and performance? Consider thinking twice what you will be using your mod for. Most people enjoy sub ohm vaping in the 50 to 100 watt range. A single 18650 might be enough. Or, you might want a dual 18650 box mod to take advantage of the extra battery capacity. If you are a cloud chaser looking for power, you will probably be interested in a triple 18650 box mod or even a quad mod.
High Wattage Vape Mods
High watt vapes and tanks offer vapers the most advanced form of vaping. These high-powered units can create massive clouds for the cloud-chucking crowd, while also delivering a precision vaping experience.
They are typically dual 18650 vapes or even triple 18650 units. High-performing mods use the latest in vaping technology to both refine the vape, and keep vapers safe with several safety protections. They feature the highest-quality build materials like zinc alloy or stainless steel.
Now we will take a look at some of the other best vape mods out there. Our top four were determined based on quality, durability, diversity, value and just how amazing the vape. Any of our top four truly bring a superior and reliable vapor experience. As we move forward, we will be looking at more specialized box mod vape devices. By that, we mean the type of performance and vaping that they accommodate. For example, if you are a serious cloud chaser using ultra-low resistance coils, then you may want a very powerful mod that can be vaped at well over 200 watts.
If you like temperature control vaping, you will want the best temperature control box mod. Whatever your individual vaping style, we want to help you find the best box mods to match. Some of the mod styles include: Single 18650 mods (up to 80 watts), Dual 18650 mods (up to 220 watts), Triple 18650 mods (250 to 300 watts), Quad mods (work with four 18650 vape batteries, can hit 350 watts), All in one vape mods (AIO systems), TC mods (temperature control vaping), DNA mods To kick things off, let’s have a look at the top-ranked portable vape mods. These are the single 18650 box mods as well as devices with internal batteries that are more compact in size.
Most Vape mod starter kits are dual batteries and operate with two 18650 vape batteries. They are a size up and heavier than single 18650 box mods. The typical wattage range of a dual 18650 vape mod tops out at about 220 watts. This is perhaps the most common type of vape mod. The best dual 18650 box mods have excellent chipsets for accuracy and responsive vaping. This class of mod can accommodate a variety of vaping styles. You should be aware that for a mod to achieve 200 watts or more, most will need at least 30 amp batteries.
If you vape at 75 to 100 watts, a dual 18650 will have the cell capacity to vape all day long and then some. If you vape at wattages in the 150 to 200 watt range, you will want to carry and extra set of fully charged batteries with you.
Not many people vape regularly at 150 to 200 watts. It is more common to vape at 75 to 100 watts and then occasionally crank up your mod to put on a cloud show. In other words, you may not use 200 watts very often, but it’s nice to know that you can dial it up if you want to.
Being an electrician is not necessary to vape, but if all these electrical terms get confusing, so it’s better to know the difference between amps, watts, and volts.
The next segment of the best box mods listings includes the top-ranked dual 18650s.
Squonk mods are box mods that use an internal reservoir of e-liquid instead of an external tank. Users squeeze the plastic bottle to send e-juice through a 510 connection to a “bottom-fed” atomizer.
Squonk mods work best with rebuildable tanks. They cut out the need to drip or refill tanks the traditional way. Squonk mods are convenient and easy-to-use. They allow users to take advantage of increased e-juice capacity because of the bottle inside the mod. Squonk mods are not new.
Custom-made squonk mods first appeared in 2010. They were popular among hardcore vaping enthusiasts for a while. Vape companies started coming out with their versions in 2015. Now, squonk mods are among the most popular versions of box mods.
DNA vape mods are highly regarded for amazing accuracy, performance, and battery efficiency. The DNA is the chipset made by Evolv. Many in the industry consider the DNA board to be the best in the business.
The accuracy of a DNA chip refers to how much power is delivered to the atomizer. If you set a DNA mod to 60 watts, 60 watts is what you get every time. A very smooth and steady 60 watts. Some mods fluctuate, DNA mods do not. This is meaningful to your vaping and your wallet. A DNA mod can help you get the maximum coil life possible.
DNA mods are sought after for their laser precision temperature control vaping as well as exceptional vaping performance. The best DNA box mod is the Vapecige VTBox DNA250C.
Small Vape Mods
Small vape mods are, well, compact vape mods! The better question would be why would you want a portable box mod? What are the advantages? The biggest advantage is portability and convenience. Many vapers have a big quad 18650 mod they use at home and on weekends, and a tiny box mod vape that they use during the week for day-to-day use.
If you want a portable, easy-to-use device, there are plenty to choose from. A small vape mod or box mod can still have all of the features and functions or their larger counterparts. The only drawback would be that, inevitably, there will be less cell capacity.
We have two recommendations when using a compact vape mod:
If you are looking for a compact box mod for all-day vaping, use an atomizer resistance of at least 0.5 ohms and vape at no more than 40 watts. This way you should have enough battery life to get you through an average workday. Portable mods with internal batteries would be suitable as well.
If you are looking for a tiny vape mod and want to vape lower resistance atomizers at higher wattage settings, look for a single 18650 device and carry an extra fully charged battery with you. The extra battery is your assurance that you will have enough battery juice to get through the day.
Here are some of the best small vape mods. Some are single 18650 and some have built-in batteries:
What are the advantages of a box mod vape? The simple answer is power and control. The best box mods and vape mods are designed to put power and control in your hands so you can dial in your ideal vaping experience. Of course, mods are larger than typical e-cigarettes and can be more complex to use, but you are trading up for performance. The vaping satisfaction and vapor production are the end goal.
Customize your personal vaping experience
Another box mod vape advantage is the enormous range of choices available to you. The competition for the best box mod is intense. You know who wins that competition? You and me, that’s who. We do. The consumers. The vaping industry is a place where the free markets work because no one has a monopoly.
Mods With Built-In Battery Vs. Separate Battery
Box mods can come with either a built-in battery or operate using separate batteries.
Built-In Battery Pros and Cons:
No need to buy separate battery or charger
Solid construction, no removable battery door
Device is lost when battery wears out (1 yr average)
When battery dies, you have to stop vaping and recharged
Separate Vape Batteries
Extend life of device
Can swap batteries when low
Large choice of batteries
Requires purchase of separate battery charger
Charging Vape Mod Batteries
To charge a built-in, internal box mod cell, simply connect the mod to a USB port. Depending on the battery capacity, it will take two to three hours to charge fully. Charging your separate 18650 vape batteries is a different matter. The vast majority of the best box mods all have a port that you can connect the device to a USB for charging. We do not recommend charging your vape batteries inside your mod. It is better to use an external battery charger.
We consider vape mods with firmware upgrades a pro. A firmware upgrade is when you connect to the manufacturer’s website, connect your mod to your computer via the USB port, and download the latest operating software into your vapor mod device. Two examples of a firmware upgrade may be expanding the power output of a device or adding another function such as TCR temperature control.
Firmware upgrades allow you to implement the latest vaping technology into your existing box mod. That way you get the new technology but do not have to buy a whole new device.
While mods with upgradeable firmware are a nice bonus, it is not necessarily a reason to buy. Look at it as a plus. If you are someone who likes to experiment with different styles of vaping and love the gadgetry of vape mods, then this would probably be a bigger deal to you. At the end of the day, upgradeable firmware is an example of another technology available to you as a vaper.
Mods With Custom Firing Profile (Power Curve)
Some of the best box mods will offer a custom firing profile. In some mods, this feature is also called a power curve. This means that you will have the ability to program up to ten seconds of atomizer firing. Here’s how that works and why you might like it.
There are usually two different ways to create a custom firing profile. One way is to connect your mod to a computer or your cell phone, sometimes by wi-fi. The other way is to program the profile on the device itself. Both methods work.
A custom fire profile allows you to program the wattage output for each second that you are pressing the fire button. As an example, you might program the first second to fire at 85 watts, the second to fire at 60 watts, the third second to fire at 50 watts, and then 40 watts for the remaining six seconds. That way you get an initial hard hit that mellows after the first couple of seconds.
Conversely, you can program a custom fire profile with a very mellow initial hit and gradually ratchet up the vapor intensity. If you like a consistent power output with no variation, then you probably would not have much use for the custom fire profile and would be better suited to normal variable wattage mode.
Most vapers fire the atomizer for about four seconds when vaping. You might not actually use all of the ten seconds of a custom atomizer fire but the option is there.
Wrapping Up Our Box Mods Guide
Vape mods are devices that look like a box! Some box mods are extremely elegant. “Regulated” means there are several customizable setting, that allow you to adjust wattage, voltage, and temperature to find your perfect vaping experience. Most vape mods on this list work with 18650 batteries.
Choosing the best box mods can be very confusing. There is a huge variety and they all generally look the same. It’s what is inside that counts. There are too many low-quality units using poor quality materials and flawed firmware. This is why we have put together a list of the best vape mods in different categories. Regardless of your vaping experience or needs, you’ll find something that fits the bill.
Published: June 15, 2019Updated: July 7, 2021
Vape Mod Reviews
Box mods are the penultimate machines for portable vaping. They occupy the leading place in the vaporizer food chain and offer plenty of customizations for advanced vaping. Meant to satiate every cloud-chasing dream, box mods are designed to extract complex flavors out of the e-juice. Our reviews are based on parameters like user-friendliness, vapor quality, durability, design, and value for money.
The VooPoo Drag X and Drag X Plus vape mods are reliable well-built products that can be depended on to provide high cloud production and excellent flavor every day.
Being a regular Sweden student, I discovered innovative ways of living healthier. And with my very first e-cigarette, I’ve got obsessed with all things digital. So vaping collided my interests in electronics, science, and health. I enjoy bringing people into the world of vaping through my reviews, guides, and best-of lists.