Ever since hydrophobic down was introduced to the industry, synthetic bags have felt a little marginalized by the new crowd of uppity goose fluff.  That said, there are times when all of the hydrophobic polymer in the world isn’t enough to keep down dry and that’s when you need a good synthetic bag.  I’ve found plenty of those moments with the Therm-a-Rest Saros 20 sleeping bag.

Therm-a-Rest Saros 20 Features:

  • Zoned insulation for weight management
  • Efficient Comfort system for easy movement
  • Proprietary eraLoft insulation, 1lb 15oz fill weight
  • 30D shell fabric with DWR
  • SynergyLink mattress connectors
  • Total weight: 2lbs 15oz
  • MSRP: $190.95


Stay dry, stay happy in the Saros

When it comes to getting a good night’s sleep on the trail, few names are more respected than Therm-a-Rest.  Their sleeping pads have kept me warm and comfortable for years, but this is actually the first time I’ve had the opportunity to test out one of their sleeping bags.  They have a whole range of down bags but the Saros is their only synthetic bag.  It’s a nice, affordable bag but it’s been built with very durable fabrics and a whole lot of know-how.

As far as total weight goes, the Saros comes in right in the middle of the pack.  It’s almost a pound lighter than the comparable Marmot Rockaway 20 which clocks in at 3lb 13oz; compared to the Mountain Hardwear Lamina 20, it’s almost identical to the Lamina’s 2lb. 14oz weight; finally, compared to the Moutain Hardwear Ultra Lamina 15, it’s rather chunkier than the Ultra Lamina’s 2lb 15oz weight.  The Saros falls right in the middle of the pack but, as I said, it’s built with some very durable materials.

Therm-a-Rest Saros 20 Sleeping Bag Review

For the face fabric, Therm-a-Rest chose a strong 30D nylon weave that’s been treated with a DWR.  This dense weave coupled with a water repellant treatment offers a lot of protection against condensation and, to a degree, wet tent walls.  The liner fabric is actually 70D which seems a little excessive – that said, it’s still very soft and feels nice against the skin.  The whole bag has a refined handle and the fabric is quiet and smooth.

One of the Saros’ unique traits is that it’s completely uninsulated on the spine of the bag.  It’s just a simple sheet of the 30D nylon and it’s designed to shed pounds.  Since the insulation underneath your body just gets compressed by your weight, it’s very ineffective at keeping you warm.  The Saros’ solution is simply to cut that out all together, but it means that you need to be very confident in your pad system.  I used the Big Agnes Q-Core SL which has an estimated R value of 4.5 which kept me warm and comf0rtable on Mt. Baker’s snowy Sandy Camp.

Therm-a-Rest Saros 20 Sleeping Bag Review

I really appreciate Therm-a-Rest’s approach with leaving the bottom of the bag uninsulated; they’ve taken pains to ensure that the bag functions perfectly with a good sleeping system.  To this end, they built in what they’re calling ‘SynergyLink’ mattress connectors.  This is simply a fancy name for two elasticized fabric loops that hold the bag on tight to a pad.  This is one of the better designs I’ve seen for keeping a bag attached to a pad – it won’t rip easily like a nylon sleeve, and they’re elastic enough to accommodate a wide range of pad sizes.  Overall, this is my favorite feature of the bag.

Beyond big-picture performance, it’s equally important to nail all of the nitty-gritty bits of a good sleeping bag.  The Saros has a two-way, full length zipper and a modest anti-snag panel that still manages to snag fairly regularly.  I thought that the draft tube was sufficient but, perhaps, on the skimpy side – it seems like synthetic bags never do this very well though.  The hood and face area is utilitarian but effective, with non-differentiated drawcord adjustments and a very simple collar.  It definitely takes some cranking to get a snug fit and I’d be tempted to call the hood area one of the weakest parts of the bag. That said, with a warm hat I was able to happily weather temperatures down near the lower limit of the bag’s 20 degree rating.

Therm-a-Rest Saros 20 Sleeping Bag Review

Lastly, I’d call the Saros true to its temperature rating.  The eraLoft compresses reasonably well and offers a surprising amount of insulating ability for its mass.  The Saros was my companion everywhere from snow camping  near Tuck and Robin lakes to Okanogan National Forest to Mt. Baker.  It’s a versatile bag with all of the wet-weather chutzpah to pull through any wet night.

The Good

  • Great pad attachment system
  • Uninsulated spine saves weight, bulk
  • High-quality face and liner fabric that’s durable yet refined
  • Bag is true to its temperature rating

The Bad

  • Average zipper track
  • Mediocre hood and drawcord design

The Bottom Line: Therm-a-Rest Saros 20

I requested this bag because I’m spending the summer working with youth in the outdoors – we take kids from the city on mountaineering and backpacking trips all throughout the Northwest and, frankly, they’re awful about letting moisture get in the tent.  The Saros 20 spent time wallowing in some of the lousiest tent conditions that I’ve seen and, frankly, it came out shining.  If it survived and thrived in the conditions that I’ve put it through, it’s going to be more than enough for just about any adventurer.

Buy Now: Available from Backcountry.com


About Author

Kevin Glover is an outdoorsman living, climbing and biking in Spokane, WA. Originally from the Nevada high desert, he moved to the PNW for its mild winters and allergen-free summers. He has guided throughout the Cascades and Enchantments for Peak 7 Adventures.

Leave A Reply