Thermarest Trail King SV Fast Self-Inflating Mattress Review

The Thermarest Trail King SV uses a unique fast inflation valve and is paired with a self inflating foam core to absolutely minimize effort and setup time. Paired with interlaced channels of thick air channels, it promises to be a simple, cozy backpacking sleeping mattress. Can it hold up under pressure? This is my review.

The Trail King SV is built primarily from a self-inflating foam with Thermarest’s proprietary AirFrame Construction. The urethane based foam core essentially has slices cut out of it that are replaced with sealed channels of air. This reduces the weight of the pad by removing extraneous material, but also increases loft by allowing air to fill in the zones, lifting the pad higher off of the ground, absorbing lumps and rocks below. The outer fabric is a combination of rugged 75D polyester for the bottom, and a lighter and more pleasant to the touch 50D print polyester for the top. The speed valve is centered at the top of the pad and acts as a clever air intake which allows massive amounts of air to be taken in at once from just a small puff of air. A more traditional valve sits off to the side for more precise adjustments and firmer inflations. The pad comes in at 2.5″ thick, 72″ long, and 20″ at its widest, with a mummy style tapered head and foot. It weighs 1 lb 13 oz and retails for $129.95, with a larger size being available at 2 lbs 6 oz with more generous 25″ x 77″ dimensions.

Big Agnes Trail King SV

What I liked

The speed valve included on this mattress is quite incredible and makes setup fary easier than any pad I’ve ever used. Simply roll out of the pad, letting the self-inflating foam inside do most of the work, then open up the speed valve. After blowing inside from a short distance 3 or 4 times it’s ready to use. It works by creating a pressure differential which not only fills the pad with your breath, but also the surrounding air. Essentially, each breath pulls in several times more air than is actually exhausted through the valve. A simple roll top creates a leak free seal, and the secondary valve is there for fine tuning or for a stiffer inflation with a little extra lung power. Watching the pad inflate without going flat while just blowing in the general direction of the valve is nothing short of amazing. Inflating the pad using the valve never once left me feeling out of breath or dizzy from basically hyperventilating into the mat. It’s a very clever system that works amazingly well and has to be experienced to be believed fully.

Big Agnes Trail King SV

The repeating channels of foam and air creates a very comfortable sleeping surface. The air channels create extra loft, so rocks, roots, and the generally misshapen earth below are not felt at all, and the soft, compressible foam beams creates a true, weight distributing mattress. Where air channels alone don’t really compress or shape to the body, the foam acts and feels similar to memory foam, just a bit more sturdy. It does an excellent job of relieving pressure points on joints, especially the shoulders, hips and back. I’ve tested the AirFrame suspension on several pads now, and it’s always provided me with an excellent, consistent night’s sleep with minimal tossing and turning, whereas air channels alone usually leave me stiff, sore, and often times worse feeling when I wake up than I did when I went to sleep. Sleeping on the mattress feels natural, with the channels providing just the right combination of cushion and support, with a little adjustment. The centralized band of foam that runs the length of the pad is great for those who have back issues too, as it creates a smooth, consistent substrate for the spine to be cradled and properly supported. Overall, it’s a very comfortable sleeping mattress.

Thermarest is well-known for their high quality construction, and that tradition certainly continues here. The exceptionally durable exterior, especially the 75D polyester bottom, has held up great. I’ve used it in dirt, grass, on stone, and of course inside the smooth floors of tents, and so far it’s showing no signs of wear or tear. The valves do an excellent job of locking down tight with no leaks, and so far as expected I’ve had no issues with leaks in the fabric either. I own several pads from Thermarest that use the same materials used here, and I’ve never had any issues with them, even after several years of consistent use in a huge range of conditions. In my experience, Thermarest makes some of the most durable mattresses, and the Trail King doesn’t disappoint.

Time after time, the self-inflating foam always returns to its original shape. After having it stuffed into a pack and compressed tightly for weeks at a time, upon opening up the valve and unrolling it, it always manages to spring back to life in its original shape with no issues.

The shape of the mattress/speed valve acts a bit of a pillow, adding a just little extra loft when positioned under a pillow, or can act as a curb to help keep a pillow in place. It’s not thick enough to serve as a pillow alone though.

Despite the relatively low r-value of 1.8, I was easily able to stay warm down to 40 degrees F, making is a viable 3-season option. While I didn’t pick up on any cold spots, I suspect that going below 35 degrees F would start to get a little chilly, as the air channels themselves don’t do much to insulate.

Big Agnes Trail King SV



What I didn’t like

The thick, lusciously padded design does result in some extra weight and bulk. At 1 lb 13 oz, it’s certainly light enough for backpacking given the rest of your gear is fairly lightweight, but there are many offerings in the price range that have a much lower weight penalty, albeit it with a certain sacrifice to comfort in exchange. The pad also packs down a bit larger than I would like, with the foam providing a certain amount of resistance when compressing/shaping it down how I would prefer. It packs down to about 12″ x 17″ with a little effort, but I found it more useful to squish it down to a flat keyboard like shape, folding it and laying it into my pack that way. This way I could slide it against the spine of my pack, or even wrap it around my compressed sleeping bag in a “U” shape with the bag in the middle. I recommend kneeling on the pad, squeezing all the air out, and closing up the valve to help keep it into the shape it’s been folded into, at least while packing it into a pack. Long term storage should be done with the valve open, which takes up some extra room too as the foam recovers to its original shape.Even with a little extra effort, it’s going to take up about double what most air channel pads would. It’s a perfectly feasible size and weight, but it’s on the higher end of appropriate, but a worthy sacrifice for comfort.

Big Agnes Trail King SV


I can’t count the times I’ve been puffing and wheezing at camp, ejecting precious oxygen into a sleeping pad that seemed to take days to inflate, dizzy from the effort. Given the Trail King SV completely eliminates this trial of asphyxiation from my camping experience with its combination of self inflating foam and Speed Valve technology, it’s a welcome addition. It’s fast, effortless, and makes setting up camp far less of a chore. The interlaced foam bands and air channels provide an exceptional sleeping experience, mostly eliminating the sore shoulders and hips that pure air channels often result in, and it’s warm enough for 3-season use in many climates. It’s light enough and packable enough to be a viable option for multi-day trips, but those with limited space or more fastidious weight requirements might be turned off from its bulkier frame. It’s built to last, easy to use, and comes in at a fair price, making it a solid option for all but the most dedicated gram counters.


For more information on Thermarest and their wide range of gear, check out their website,

For information on our rating system and our testing procedures, check out our About us/ Contact us page.

I want to extend a huge thanks to Thermarest/Cascade Designs for providing this product for review. We couldn’t do it without their help. Our full disclosure can be found here.

Thanks as always for reading! Don’t forget to follow our blog for future updates and reviews. If you have any questions, comment below, send us an email, or find us on Twitter or Facebook (links on the right).


4 thoughts on “Thermarest Trail King SV Fast Self-Inflating Mattress Review

  1. SO IRRITATING~! The different chambers always break so you end up on a lopsided bed with a huge bubble on one side where two chambers have combined to try to throw you out of the bed. Happened after just a couple days.

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