Therm-a-Rest Vesper 20 Review

February 27, 2019
Therm-a-Rest Vesper 20
Therm-a-Rest Vesper 20 ThermarestVesper_01 ThermarestVesper_02 ThermarestVesper_03 ThermarestVesper_04 ThermarestVesper_05 ThermarestVesper_06 ThermarestVesper_07 ThermarestVesper_09 ThermarestVesper_010 ThermarestVesper_011

The Good

  • Superlight
  • Compresses into tiny package
  • Water resistant down
  • Huge neck baffle with snap closure

The Bad

  • No Hood
  • Open back
It was a very close call between the ZPacks Classic Sleeping Bag and the Therm-a-Rest Vesper for our Best in Class award. Both are lightweight hoodless backpacking quilts and both compress to a very small size. The Vesper comes with a compression sack that cinches it down to roughly the size of a water bottle. Ultimately the ZPacks bag won by one point because it is a little bit warmer, but we love the Vesper. It does not have a zipper and features a fully open back with a huge draft collar with a secure snap. It is packed with Nikwax Hydrophobic down, and we did put this to the test. After getting doused by rain and remaining warm in the Vesper, we can vouch that this water-resistant coating works.

New for 2019, the Vesper is a backpacking quilt from Therm-a-Rest. It has no hood and no zippers, which reduces weight and bulk. The foot box is contained, but the back of the bag is completely open. This can either be left open to circulate fresh air, or it can be tucked underneath the sleeping pad and secured with straps.


At 1 pound 4 ounces, the Vesper is the second lightest product in this review, after the Feathered Friends Tanager. For ultralight backpackers, this is a huge draw. The Vesper has a minimalist design that is appealing for those who want to travel as lightweight as possible. This means it skimps on some comfort features, but the user is rewarded with less weight to carry.


Gone are the days when a sleeping bag took up one-third of your pack space!

Perhaps the biggest stand-out feature of the Vesper is its compressibility. It comes with a tiny compression sack and stuffs down to a size that is just slightly larger than a Nalgene water bottle. When each of the bags in this test was packed into the stuff sacks that came included with each bag, the Vesper and the Sea to Summit Flame III were tied for the smallest bundles. The compressibility, low weight, and warmth are attributed to the high quality 900-fill down that is used to insulate the Vesper. This ultra-lofty and ultra-compressible insulation is top-of-the-line.


Our lead tester was set to dislike the Vesper. She took it with her on a multi-day backpack into Wyoming’s Wind River Range, complete with rain and cold nights, and she expected to miss a regular hooded mummy bag. It turns out that she was pleasantly surprised with the warmth and comfort of this bag, even in the nontraditional shape.

The Vesper is designed with box baffles, so there are no sewn-through seams. This eliminates any cold spots other than the open back of the bag, which will usually be tucked around a sleeping mat. It is not nearly as lofty or as warm as the ZPacks Classic Sleeping bag (this is obvious at first glance) but it is still a warm and cozy bag. What our testers felt made this bag exceptional is the super thick draft collar with a snap and cinch. If the collar is cinched and secured, the draft collar sits inside, curling around the neck and shoulders. This made a much bigger difference than we anticipated, and made the bag feel cozy even on stormy nights.

The lining material on the interior of this bag uses Therm-a-Rest’s proprietary Thermacapture technology. This is a reflective coating that redirects heat back towards the body, preventing it from being lost to the outside air. When you look closely at the lining you can see that it is shinier and greener than the shell material. This helps keep its occupant warm through the night.

Since it lacks a hood, it is best slept in while wearing a beanie, a Buff or fleece gaiter over the ears, or a fleece with a hood. In really cold temperatures, wear a down jacket with a hood to keep warmth around the head.


Quilts allow for the most versatility in terms of ventilation. Without a zipper, the shape of the Vesper allows for freedom of movement and arrangement. The feet can be tucked into the footbox for warmth, but the top of the blanket can be tossed back if the sleeper gets starts to feel sweaty. The lack of a hood allows for a more open, less stuffy way of interacting with the sleeping bag.


Unlike the two bags that most closely compete with the Vesper, this bag has hydrophic treated down. We love both the ZPacks Classic Sleeping Bag and the Feathered Friends Tanager for their low weight and clever designs, but the Vesper is the bag we would want to be in if getting wet was a possibility. And in fact, we did get wet while testing the Vesper. On a summer backpacking trip in the Wind River Range in Wyoming, our tester got caught in an infamous Wind River storm that toppled her tarptent. Her sleeping bag got soaked in the process. She fully intended to spend the rest of the night cold, wet, and miserable. After she got her tent restaked, she climbed back into the Vesper and miraculously, it was warm and dry. The hydrophobic treatment did its job and repelled water so the down could maintain its loft.

We already mentioned that the thick draft collar combined with a drawcord and snap are key features that contribute to the warmth and comfort of this bag. The other feature of note is the Synergy Link system along the back of the bag. This consists of thin, stretchy straps that connect to each of the open sides of the bag. These are intended to wrap around the back of the sleeping mat, both to prevent the sleeper from rolling off of the mat in the middle of the night and to keep the open back of the sleeping bag tucked around the person all night long. The footbox is still left free, and the straps are just loose enough to allow for rolling around and side-sleeping while still keeping everything in place.


The Vesper is made with soft-to-the-touch 10-denier fabric – a delicate material – that gives the bag its light and airy feel. Even while using this bag on multi-day trips in rugged weather, we did not have any rips, tears, or durability issues. Since there is no zipper on this bag, there is no danger of the zipper failing, which is often the first thing to go. Bags designed with box baffles tend to last longer than ones made with sewn-through seams, so we anticipate that this bag will last several seasons.


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