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Therm-a-Rest Saros 20 Review

A comfortable bag that's borderline too heavy for backpacking
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Therm-a-Rest Saros 20 Review
Credit: Therm-a-Rest
Price:  $210 List
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Manufacturer:   Therm-a-Rest
By Jack Cramer ⋅ Review Editor  ⋅  May 19, 2019

Our Verdict

Designing a backpacking sleeping bag is a tricky balancing act between warmth, comfort, and weight. In the case of the Saros, we believe the balance is tipped too far in favor of warmth and comfort. It's certainly both of these. In achieving this warmth and comfort, however, it unfortunately became heavy and bulky. Its 3.84-pound weight is heavy enough that we don't consider it a great choice for backpacking. The Saros is still an impressive sleeping bag, but it's better suited for activities where it's carried by a boat, car, or draft animal, rather than your throbbing shoulders.
Super comfortable
Excellent build quality
Foot warmer pocket
Super heavy
Extremely bulky
There are cheaper bags for car camping
Product Updated
The updated Saros, pictured above, features Therm-a-Rest's W.A.R.M. Fit technology, which stands “With Additional Room for Multiple positions”. This design is intended to retain thermal efficiency while allowing a bit more space for various types of sleeping positions. Aside from this, the updated bag remains very similar to the model we tested.

Our Analysis and Test Results

Therm-a-Rest is deservedly known for making outstanding sleeping pads. Their sleeping bags, however, have yet to earn a similar reputation. We recently tested their comfy Saros and ultralight Hyperion models. Both are impressive but still a step behind our favorite bags in their respective categories. Read on to learn why the Saros missed out on a budget sleeping bag award.

Performance Comparison

therm-a-rest saros 20 - therm-a-rest has mastered backpacking sleeping pads. however, they...
Therm-a-Rest has mastered backpacking sleeping pads. However, they seem to still be figuring out sleeping bags.
Credit: Jack Cramer


The Saros contains 39 ounces of synthetic eraLoft insulation. This amount is considerably more insulation, by weight, than most backpacking sleeping bags. Unfortunately, however, this insulation doesn't make it considerably warmer. Its 20°F lower limit rating (EN) seemed accurate compared to other bags. This rating, however, doesn't set it apart from its competitors and we consider several bags to be warmer.

therm-a-rest saros 20 - en tested bags receive three ratings: a comfort, limit, and extreme...
EN tested bags receive three ratings: a comfort, limit, and extreme rating. Most users will be happy near the comfort rating. Staying comfortable at the limit rating usually requires a quality sleeping pad and good layering.
Credit: Jack Cramer


A consequence of this bag's ample insulation is that it's disappointingly heavy. On our digital scale, a size long weighed 3.84 pounds. This figure is more than double that of the lightest budget sleeping bags. It is heavy enough that we recommend the Saros primarily for car camping and only occasional backpacking.


One thing this bag has going for it is its comfort. It has some of the roomiest dimensions of any mummy bag. We're also big fans of the 20-denier polyester taffeta fabric, which manages to be glossy while still feeling soft. The Saros also has a foot warmer pocket to keep your toes cozy. The comfort could be slightly improved, however, if the hood drawstring were an elastic cord rather than a shoelace-like string.

therm-a-rest saros 20 - compressed inside its stuff sack, the saros is still too big to fit...
Compressed inside its stuff sack, the Saros is still too big to fit across the bottom of this large 75-liter backpack.
Credit: Jack Cramer

Packed Size

Another consequence of this bag's ample insulation is its bulky packed size. Using an after-market compression sack, we weren't able to squeeze it any smaller than 15.5 liters in volume. That means it's more than double the size of the smallest budget sleeping bags. The simple drawstring stuff sack that it comes with is also an unfortunate shape that won't fit horizontally across the bottom of most backpacks.


The Saros features a ¾-length main zipper that's okay at venting excess heat. It also has a fluffy neck baffle that's good for sealing heat in on frosty occasions. The synthetic insulation can be relied upon to maintain its ability to insulate if it gets wet. This bag, however, would score a little better in versatility if it had a longer zipper or another way to let heat escape on warmer nights.

Features and Design

This bag has perhaps the most accessory features of any budget sleeping bag we tried. Some of these are useful, others not so much. Many of our testers, for example, consider the sleeping pad attachment system unnecessary, but thankfully, it's removable. The stash pocket, in contrast, is an accessory feature that we happen to like for keeping a headlamp or phone handy.

therm-a-rest saros 20 - the saros has a zippered stash pocket on the right side of the bag.
The Saros has a zippered stash pocket on the right side of the bag.
Credit: Jack Cramer

Finally, the foot warmer pocket is a polarizing accessory. Some of our testers are rather fond of it. Others found it entirely unnecessary and thought it would be smarter to move the extra insulation closer to your core rather than your extremities. With that said, it's up to you to decide if a small insulated sleeve to tuck your feet inside is desirable.

therm-a-rest saros 20 - our review team believes the saros is too bulky and heavy for...
Our review team believes the Saros is too bulky and heavy for long-distance backpacking. However, it's great for car camping or shorter hikes near the trailhead.
Credit: Jack Cramer


Although the Saros doesn't provide great weight or packed size performance, it has high-quality materials and construction. Many of our testers think its accessory features are a bit much, but there will be plenty of consumers that feel the opposite. For those that can fully appreciate its extra bells and whistles, it offers a decent value.


There's a lot to like about the Saros. It's undeniably comfortable and fitted with some clever accessory features. We are also impressed with the quality of its materials and construction. However, to supply this comfort and include these accessories, it becomes disappointingly heavy — so much so that we think it's too weighty for frequent backpacking. The Saros is still an awesome bag for car camping or short hikes, but you'll probably want a lighter, more packable bag for true backcountry overnights.

Jack Cramer