REVIEW: Therm-a-Rest Trail King SV Mat

Lighter mats tend not to be the most luxurious, so in contrast to more spartan offerings, Therm-a-Rest have gone all out for comfort here. Richard Prideaux enjoys a restful night's sleep on this beefy mat designed with car campers and basecamps in mind.

I thought this sleeping mat business had been cracked. You can have thin foam if you're a minimalist, thick self-inflating foam if you camp next to a car, and something in between if you don't want to completely sacrifice comfort but still need to carry it on your back. Surely this roll of green nylon from Therm-a-Rest can't offer me much more? But in fact, the Trail King has proved to be pretty much the most comfortable mat in my store cupboard. Its method of inflation is interesting, too. But minimalist, this is not.

It's luxuriously thick, but has a weight to match..., 129 kb
It's luxuriously thick, but has a weight to match...
© Richard Prideaux

I've got loads of sleeping mats. Loads. They are stacked up behind my wardrobe and rolled up in the gear store. I've got foam slabs encrusted with mud and gravel from somewhere in Europe (or further afield) that are difficult to kill but offer limited comfort. I've got decade-old self-inflating mats that no longer self-inflate, and need artificial respiration through a grime-encrusted valve to perform. There are the modern style mats without any foam but lots of air – colder, but lighter and they pack down to a small size.

Taking it wild camping in foul Snowdonia weather, 120 kb
Taking it wild camping in foul Snowdonia weather
© Richard Prideaux

This Therm-a-Rest Trail King SV is something of a hybrid – it self-inflates, there is foam inside but there are also air channels. Held up to the light it looks like the skeleton of a trout with ribs of foam falling either side of a foam spine. They're calling this AirFrame Construction. Fair enough.

At one end there is the familiar screw valve on the corner and also a strange drybag type closure. This is called the SpeedValve and on opening, it reveals a kind of rubber gusset. A drawstring storage bag completes the set.

At £110.00 it sits at the upper end of the pricing spectrum, but not unexpected for this brand and their pedigree.

Fishbone-like structure of the 'AirFrame Construction'
© Richard Prideaux

Drybag-style rolltop closure
© Richard Prideaux

Overall impressions

This isn't the lightest of mats on offer from the Therm-a-Rest range. The Regular length weighs 830g, so it sits very much at the pie-eating end of the scales. I'm not sure how much of this is down to the SpeedValve itself – the plastic buckles and thick edge on the drybag-style closure must add a substantial amount of weight. This is a very thick mat (6.3cm), so a little under twice as thick as the Prolite Regular and the extra material to wrap all of that must account for some of the rest of the bulk. Its depth also makes it very comfy, of course!

Out of the bag and unrolled on the floor it's clear that the new valve has made a difference. You can see the mat expanding in seconds and it reaches equilibrium very quickly. Next you slightly open the two sides of the opening and blow into the void, increasing the internal pressure. The black rubber gasket prevents it all coming straight back out at you. With the SpeedValve closed in the same style as a drybag the mat is pretty much ready to go although the second, traditional valve can still be used to top it up.

This video from Therm-a-Rest explains how to use the SpeedValve:

Packing down is easier than with most mats – open the valves and roll it up. I've managed to roll it down to an acceptable size on the first go most of the time, and I've stored it with the SpeedValve open and the gasket inverted to allow moisture to escape. It is still fairly bulky when rolled up – though perhaps not unacceptable for the thickness of the mat.

Use and abuse

The 'SpeedValve' is basically a rubber gusset that lets air in, but not out, 79 kb
The 'SpeedValve' is basically a rubber gusset that lets air in, but not out
© Richard Prideaux

It's quick to inflate, and has a secure rolltop closure , 97 kb
It's quick to inflate, and has a secure rolltop closure
© Richard Prideaux

I've bedded down on this thing three times now – once in a tent somewhere on a soggy patch of Snowdonia and twice in the Welsh forests. Each time it's done what I wanted it to do, and has kept me aloft and insulated all night. It has also put up with being laid directly on pointy sticks and stones under my not insubstantial weight (it's my bones, I swear).

As mentioned it does take up more space in my bag than I would like, but it is also pretty much the most comfortable sleeping mat in my stores. It is quick to use, and can be set up immediately rather than lying there slowly inflating whilst I go off to do something else.

I have the Regular length, which is 182cm long. This was just long enough for me without dumping my feet on the ground. There is also a longer version which gives you an extra 12cm.

Rolling it up takes seconds
© Richard Prideaux

Finishing the job with a bit of puff
© Richard Prideaux

Final thoughts

I can certainly see where Therm-a-Rest are going with this mat. It's thick and comfortable, it's warm enough for three-season use, the SpeedValve works well and the air channels between the foam are an acceptable compromise between warmth and weight. Car camping is mentioned in the marketing material, and this would be a great mat for that purpose. As such, however, it is a little too heavy for regular backpacking and certainly takes up too much room for me.

If you appreciate extra comfort on a camp or bivvy, the Trail King rules OK, 166 kb
If you appreciate extra comfort on a camp or bivvy, the Trail King rules OK
© Richard Prideaux

With that said, there are two types of customers I can see this being an excellent choice for. The first are valley basecampers who want a comfortable mattress for the weekend car camping escapes to the National Parks but who might occasionally want to take it into the hills. The second is possibly those who need more padding for their hips due to health issues, but want something simple that performs well.

The Trail King is built to a high standard, it does what it says on the tin and it is a good compromise between comfort, packed size and performance - if you value the former over the latter two. Lightweight backpackers or mountaineers need not apply, but for car camping this mat is perfect. And for the very occasional backpacking trip where weight isn't key, it will also do the job.

Therm-a-Rest say:

New for 2017: The Fastest Self-Inflating Backpacking Mattress

By combining our SpeedValve™ technology with AirFrame™ Construction, we've created a backpacking mattress that inflates in a matter of seconds. Plus, thanks to the auto-reversing SpeedValve, the mattress deflates at remarkable speeds. This unprecedented ease-of-use is fused with 2.5 inches of ultra-supportive loft and an R-Value of 1.8, making the Trail King SV a reliable three-season mattress designed to save you precious time in the backcountry. Stuff sack included.

  • Supportive Loft: AirFrame™ construction offers 2.5 inches (6.3 cm) of high-loft support.
  • Fast Inflation: SpeedValve™ technology combined with self-inflating foam creates swift inflation.
  • Faster Deflation: Auto-reversing SpeedValve™ deflates mattress in a flash.
  • Sizes: Reg 183x51cm; Large 196x63cm
  • Thickness: 6.3cm
  • Weight: Reg 830g; Large 1.08kg
  • R-value: 1.8
  • Fabric: 75d polyester
  • Foam: urethane foam

Trail King SV prod shot, 177 kb

For more info see

Richard Prideaux head shot, 122 kb

About Richard Prideaux

Richard Prideaux is the owner of established North Wales outdoor skills training and activity business Original Outdoors. He spends on average one night per week sleeping in a forest, up a mountain or on a beach somewhere in the UK and further afield and the rest of the time teaching navigation, foraging, tracking and other wilderness skills.

For more info see

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