Exped MegaMat vs Therm-a-Rest MondoKing 3D: which self-inflating mattress is built to last

The verdict

We haven't bought or used either mattress. Every figure on this page comes from Exped's and Therm-a-Rest's own product, warranty and parts pages, read 2026-09-22, and each value in the spec table links to its source. The scores follow our Built-to-Last scoring rubric. For the whole field ranked, see our best camping mattress picks, and the camping mattresses hub collects every mattress and cot pad guide.

Side-by-side specs

Durability rows come first: fabric, warranty and parts, then warmth, size and weight. We score the MegaMat in its LXW size and the MondoKing in Large, the sizes named in each product record; other sizes are listed in the rows. A dash means the maker doesn't publish that figure.

Warranty: limited lifetime vs 5 years

Therm-a-Rest's warranty page reads: “We offer a Limited Lifetime Warranty on all products, except electronic devices,” and adds, “We operate on a repair-first model.” Exped's reads: “EXPED products carry a 5-year warranty on defects in materials and workmanship.” On our warranty band that is a 10 against a 7. Five years is a real term, not a token one. The difference is who pays when a manufacturing defect shows up in year six: Therm-a-Rest, or you.

Fabric, foam and valves

The shells are close to identical on paper. Exped uses a recycled 50D tricot polyester top and a recycled 75D polyester bottom, both TPU laminated. Therm-a-Rest uses a 50D polyester knit top over a 75D polyester bottom. Our build band scores the ground-side fabric, since that's the face that meets tent floors and gravel: 75D earns a 7 for both, and both get the extra point for a foam core, because a leak still leaves a layer of foam between you and the ground. Build durability: 8 each.

Inside, Exped specifies a 16 kg/m³ open-cell PU foam core with vertical side walls and two flat valves. Therm-a-Rest specifies StrataCore urethane foam with vertical sidewalls and its TwinLock two-valve system, and the MondoKing is made in the USA. Exped publishes a foam density and Therm-a-Rest doesn't, so there's no like-for-like foam comparison to make; we won't guess at one. One detail worth knowing before you buy: retailer listings describe the MegaMat as 4 inches thick, while Exped's own figure is 10 cm, which is 3.9 inches. We use the maker's number.

Parts and repair

Both mattresses land on the same repairability score for the same reason: you can patch the shell yourself, but neither maker lists a replacement valve for these models. Exped lists a repair kit in the box and sells a Field Repair Kit (UV glue and TPU patches) separately; its accessories catalog lists no replacement valve, and it repairs mats “with a professional team in our own workshops.” Therm-a-Rest sells its Permanent Home and Instant Field repair kits, and the MondoKing's TwinLock valve has no listed replacement kit, so valve problems go to its warranty and repair team. For damage the warranty doesn't cover, Therm-a-Rest says it “may be able to complete the repair for a reasonable fee.”

For contrast, Therm-a-Rest does sell a do-it-yourself WingLock valve kit for pads like its 2-inch BaseCamp, which is why the BaseCamp earns a 10 on repairability and these two thick mattresses earn a 5. If you want to know what a patch job involves before you commit to either, read how to find and fix a camping mattress leak.

Warmth: R 8.1 vs R 7

This is a like-for-like comparison, which isn't always true of R-values. Exped lists the MegaMat's figure as “R-Value (ASTM)”: 8.1. Therm-a-Rest's tech specs list 7 for the MondoKing 3D, and its product page FAQ cites the ASTM F3340-18 standard. Same standard, so the 1.1 difference is a real one on paper. If you see 8.0 on a MondoKing listing, that's a retailer figure that disagrees with Therm-a-Rest's current specs; we use the maker's 7.

How much does 1.1 matter? Both clear R6, where Therm-a-Rest's chart places “extreme cold.” Both clear the bar Exped sets on the MegaMat's own page: it “recommends using a sleeping mat with an R-Value of at least 6.5 or higher to ensure your sleeping bag provides the warmth it is rated for.” So the MegaMat's extra warmth is headroom for the coldest nights, not the difference between warm and cold for a typical three-season camper. On our fit band the MegaMat gets the bigger R-value bonus (+4 against +3), and the MondoKing wins it back on thickness (4.25 inches earns +2; 3.9 inches earns +1). Our guide to camping mattress R-values explains what the ASTM number measures and how R-values add when you stack a foam pad underneath.

Size, thickness and top fabric

Match the sizes before you compare anything else. The MegaMat comes in MW (72.0 x 25.6 inches), LW (77.6 x 25.6) and LXW (77.6 x 30.3). The MondoKing 3D comes in Large (77 x 25) and XXLarge (80 x 30). So the fair pairings are MegaMat LW against MondoKing Large, which are within an inch of each other, and MegaMat LXW against MondoKing XXLarge, which are the same width, with the MondoKing 2.4 inches longer. If you're tall, that matters: the longest MegaMat is 77.6 inches and the XXLarge MondoKing is 80.

Thickness is close: 3.9 inches for the MegaMat, 4.25 inches for the MondoKing per Therm-a-Rest's tech specs (a feature bullet on the same page says 4 inches of loft). Both have vertical side walls, which keep the full published width usable to the edge, and both have a soft knit top: tricot on the Exped, stretch-knit on the Therm-a-Rest.

Couples should note one real difference. Therm-a-Rest makes the MondoKing 3D only in single sizes and says it mates with other 3D mattresses. Exped sells a MegaMat Duo in a Queen size, 79.9 x 59.8 inches with one continuous foam core and the same ASTM R-value of 8.1. If one shared surface is the goal, see our camping mattresses for couples.

Weight and packed size

The MondoKing is the lighter mattress at each matched size. Large weighs 4 lb 6 oz against 5.0 lb for the MegaMat LW; XXLarge weighs 5 lb 8 oz against 5.7 lb for the LXW. Packed, the MondoKing Large rolls to 26 x 10.3 inches and the XXLarge to 31 x 10.3; Exped publishes a packed size only for the LXW, 31.1 x 9.8 inches. Both score 8 for portability in the scored sizes. Neither is a backpacking pad, and neither is meant to be: these are mattresses for the car, the tent and the truck.

Buy the MegaMat if / buy the MondoKing 3D if

Buy the Exped MegaMat if

• You camp in real cold and want the higher ASTM R-value: 8.1 against 7.
• You want the same foam in other shapes: Exped also makes the MegaMat Duo (Queen) and the MegaMat Auto, a vehicle mat 52 inches wide narrowing to 39 inches at the foot with the same R-value. For vehicle sleeping, compare it with the air options in our truck-bed and SUV mattress picks.
• You want a repair kit in the box and a maker that decides warranty by date of manufacture if the receipt goes missing.

Buy the Therm-a-Rest MondoKing 3D if

• You want the longest written promise: a limited lifetime warranty with a repair-first policy.
• You're tall: the XXLarge is 80 inches long.
• You want the lighter mattress at each matched size.
• Made in the USA matters to you.

Consider neither if

• You want the thickest, warmest mat we score. The Exped MegaMat Max has 15 cm (5.9 inches) of foam and an ASTM R-value of 10.6, at 7.4 lb and only in LXW, with the same 5-year warranty. If you sleep on your side, weigh it against the rest of our camping mattresses for side sleepers.
• You want a lifetime warranty and a little more warmth than the MondoKing. The Sea to Summit Comfort Deluxe has 4 inches of foam, an R-value of 7.7 (ASTM, per Sea to Summit) and a limited lifetime warranty. It scores 8.0, within 0.3 of the MondoKing; the catch is that Sea to Summit lists no mat parts online and handles them by request.
• You sleep on a cot and want a pad you can fully repair yourself. Therm-a-Rest's 2-inch BaseCamp has an R-value of 6 and a valve kit you can buy; see our cot pad picks.
• You're still choosing a type. Start with how to choose a camping mattress.