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Therm-a-Rest MondoKing 3D Review

Our favorite option with easy to use valves and pump sack for easy inflation
Editors' Choice Award
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Price:  $210 List | $209.95 at Backcountry
Compare prices at 2 resellers
Pros:  Warm, comfortable, easy to inflate
Cons:  Large packed size
Manufacturer:   Therm-a-rest
By Laurel Hunter & Maggie Brandenburg  ⋅  Apr 29, 2020
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#1 of 16
  • Comfort - 40% 10
  • Ease of Use - 20% 9
  • Warmth - 20% 9
  • Versatility - 10% 7
  • Packed Size - 10% 6

Our Verdict

The Therm-a-Rest MondoKing 3D was a fantastically comfortable mattress before, and some clever updates have nudged it into the winning spot of this review! It features four inches of plush foam comfort that does a stellar job insulating you from the cold ground while supporting your pressure points no matter what your preferred sleeping position is. The new TwinLock valves insure very simple inflation and deflation, and the included pump sack means you won't black out blowing it up. It is lighter than the previous version and while it also has a lower insulation value, we sure didn't notice the difference.

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Our Analysis and Test Results

Teasing out the differences between camping mattresses is really about looking at all of the details. When you are sleeping on 4 inches of foam, you are going to be comfortable, and the mattress will be insulating you from the cold ground. The updated MondoKing 3D is exceptionally comfortable and warm. However, it is large when packed (like most of the foam mattresses in this review), but it is just slightly easier to inflate and deflate, making it our new Editors' Choice.

Performance Comparison

Plenty comfortable and plenty of surface area to sprawl.
Plenty comfortable and plenty of surface area to sprawl.


Compared to your standard inflatable sleeping pad or basic air mattress, using the Therm-a-Rest MondoKing 3D is bonafide luxury camping. Vertical sidewalls mean that you can utilize the entire 30-inch width and 80-inch length to spread out and sleep like an extra, extra large king among starfish. While this may feel indulgent for camping, it is quite lovely to not feel like you are in danger of rolling off an edge of the mattress, and also provides room for your dog to snuggle nearby.

No matter your preferred sleeping position, the four-inch foam core of the MondoKing can easily be adjusted to perfect firmness with the separate one-way valves (one for "in," one for "out"). Because it is easier to release a little air with a simple twist of the conveniently labeled "out" valve than it is to add air on the fly, we recommend adding a little extra air before you settle in for the night and release air, as necessary, for the perfect level of comfort.

The updated MondoKing uses StrataCore Foam, which is essentially a thermal foam core that is sandwiched between ridges of foam and air. This give the pad a unique wave-like texture to the surface and also makes it much easier to roll up. It offers a substantial weight reduction from the previous version, as well. We did not notice the ridges at all when using the mattress.

The surface is marked with a unique ridge pattern that does not inhibit comfort in any way. The soft cover is quiet and soft.
The surface is marked with a unique ridge pattern that does not inhibit comfort in any way. The soft cover is quiet and soft.

The soft polyester cover provides a non-slippery, non-sticky place to lay a cheek that is both breathable and quiet to sleep on top of. Many of the mattresses we tested are really, really comfortable, and the MondoKing is one of the best.

Ease of Use

Probably the greatest update on the MondoKing is the new and improved valves. They are located on each of the bottom two corners of the mat, and clearly labeled IN and OUT. They are noticeably larger than the old two-way valve, meaning more air can be moved through the valves, and since they are one-way valves, they are easier to use.

The MondoKing can still be blown up by mouth, but the stuff sack doubles as an inflation sack, meaning you can blow it up without getting lightheaded! The sack snaps onto the valve and then you blow lightly into the bag (or even better, catch a breeze) and then roll up the sack to push air into the pad. We can't quantify that it is three times faster than the old system, as Therm-a-Rest claims, but it was very easy to inflate. For the initial inflation, we allowed the mattress to self-inflate for about 20 minutes. Then, using only the pump sack, it took about two and a half minutes to fully inflate.

The storage bag doubles as an inflation sack and snaps onto the intake valve for easy use.
The storage bag doubles as an inflation sack and snaps onto the intake valve for easy use.

After initial inflation, using only the pump sack to inflate, it was reliably around 2 minutes to reach full inflation. The new deflation valve means that air moves out of the mattress pretty quickly. The foam still takes a bit of smashing to roll it small enough to fit in the storage sack. The one-way deflation valve does not let air in, however, meaning it is just a matter of rolling once to get most of the air out, and then a second roll to squish it tight.

The deflate valve opens up when air is pushed out and closes up when it isn't  making deflation a much easier process.
The deflate valve opens up when air is pushed out and closes up when it isn't, making deflation a much easier process.

We found the MondoKing was easy to inflate, takes some muscle to deflate and fit back into its bag, and the bag very convenient to carry and store.


The updated MondoKing has an R-value of 7, somewhat lower than the the previous version's 11.4, which we are guessing is related to the new ridged foam interior. R-value tells you the insulating power of any given sleeping pad or camping mattress, giving you an idea of how cold of a surface you could comfortably sleep on without that coldness seeping through to your body. To winter camp, it's generally recommended that you use a sleeping pad or mattress with an R-value of at least 4. We camped out in 18 degrees and had zero complaints. If you are heading off for a sub-arctic adventure, there are a few mats in this test that are rated higher for insulation, but for four-season camping in the lower 48 states, the MondoKing should be plenty toasty. It's also just as important to note that unlike the cold-temperature rating of a sleeping bag, having a camping mattress with an R-value this high won't make you pour sweat in hot weather. This is a solid four-season camping mattress.

Plenty warm for car camping  too  where metal can be colder than the ground.
Plenty warm for car camping, too, where metal can be colder than the ground.


Based on the overall size and weight of the MondoKing 3D, this isn't the camping pad you would take on a backpacking trip. At about 5.25 pounds, you're probably not going to want to carry this mattress too far from your car or garage. It is worth noting, however, that the XXL version that we tested is actually lighter than the old version while being considerably larger.

While our testers quite adored the large surface area, two of these XXLs will not fit in the average two-person tent, which is around 50-55 inches wide. The large size is 25 inches wide, and two of those, however, will fit. While we suggest you check this against your own personal tent width, as tent styles and sizes may vary, you're much more likely to be able to fit the promised number of people in your tent by using the MondoKing 3D Large rather than the XXL. If you are car camping in full glory, however, you may very well have a much larger tent, in which case why not go all out for maximum surface area?

Packed Size

When packing the car for a weekend of camping, the MondoKing isn't too large to leave behind, and more than makes up for its size with its comfort. While we wouldn't be stoked to pile seven of them in the back of the van, the space it takes up is pretty comparable to the other highly comfort-rated mattresses in this review.

It is not tiny! But there is a handy carrying strap.
It is not tiny! But there is a handy carrying strap.


The MondoKing 3D is on the more expensive side of the self-inflating camping mattresses we tested. Despite being a decent chunk of change to throw down on a camping mattress, we think you'll find the comfort and ease-of-use of the MondoKing to be well worth the dough.


This pad combines a high level of comfort compared to all the camping mattresses we reviewed, with a new and improved valve system to make it just that much better than the others. The MondoKing 3D is an excellent all-around camping solution, and we would happily recommend it to both our dirtbag, live-out-of-my-van friends as well as our hard-to-please, princess-and-the-pea family members.

The inflation sack makes all the difference in ease of set-up.
The inflation sack makes all the difference in ease of set-up.

Laurel Hunter & Maggie Brandenburg