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Therm-a-Rest Hyperion 20 Degree Sleeping Bag

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Starting At: $412.39

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Therm-a-Rest Hyperion 20 Degree Sleeping Bag

By Troy

Enwild Gear Specialist

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The Therm-a-Rest Hyperion 20 Degree sleeping bag’s lightweight insulation and cool-weather features promise a warm sleeping experience for all of your 3-season adventures.


The Therm-a-Rest Hyperion 20 Degree sleeping bag’s lightweight insulation and cool-weather features promise a warm sleeping experience for all of your 3-season adventures.

The bag is insulated with 900 fill Nikwax Hydrophobic Down. Down insulation has long been renowned for its compressible properties and efficiency in delivering an excellent warmth-to-weight ratio. The shortcoming of down has been its susceptibility to the effects of moisture, losing much of its performance qualities when wet or damp. Nikwax Hydrophobic down insulation provides water-repellency that keeps the insulation dry longer and allows it to dry faster if it should become wet. More importantly, it maintains thermal efficiency even if it becomes wet, a quality that could traditionally only be found in heavier, less-compressible synthetic fills. Additionally, the bag has “zoned” construction, concentrating insulation on top of the bag so you have warmth where you need it most and saving weight by minimizing insulation on the bottom of the bag where it just tends to get compressed beneath the weight of your body anyway. Mesh box baffles maximize loft and minimize cold spots in key areas.

Integrated SynergyLink connectors keep your sleeping pad (sold separately) from moving away during the night. These strips are removable if not needed. A draft collar and zipper draft tube prevent cold air from sneaking inside the bag and the hood can be cinched down to keep your head insulated.

Other features include a snag-free zipper, an included compression sack, and a storage sack.

The Therm-a-Rest Hyperion 20 Degree sleeping bag comes in different sizes to accommodate different heights. Small fits 5’1” to 5’6”, Medium fits 5’ 7” to 6’, and Large fits 6’ 1’ to 6’ 6”.

  • 900 fill Nikwax hydrophobic down
  • Box Baffled construction
  • SynergyLink connectors
  • Zoned insulation
  • Draft collar
  • Zipper draft tube
  • Snag-free zipper
  • Cinchable hood
  • Compression sack and storage sack included
California residents: view proposition 65  Warning

Technical Specs

Best Use
Backpacking, Camping
En Comfort Rating
32 Degrees F
En Lower Limit Rating
20 Degrees F
Fill Material
900 Fill Nikwax Hydrophobic Down
Fits To Girth
Small: 55"
Regular: 57"
Long: 58"
Fits To Length
Small: 5' 6"
Regular: 6' 0"
Long: 6' 6"
Temperature Rating
20 Degrees F
Insulation Type
Item Weight
Small: 1 lb 3 oz
Regular: 1 lb 4 oz
Long: 1 lb 6 oz
Compression Stuff Sack and Storage Sack Included
Limited Lifetime
Packed Size
6" x 8"
Shell Material
10D Nylon Ripstop with DWR
Liner Material
10D Nylon Ripstop

6 Reviews

4.67 / 5


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Super lightweight sleeping bag


Extremely packable and light sleeping bag, perfect length for 180 cm.


maybe price?



Warm, Comfortable, Ultralight


This is a great sleeping bag. Packs down to a Nalgene 1L size bottle. Super lightweight!





Awesome Lightweight Bag


Love how small and light this bag packs down to. Come with both stuff sac and storage bag. Pad straps are a plus.


The bag is a little more narrow than typical mummy bags but I knew this before I purchased so no issue for me.



Sturdy & light (as a feather)


After being tired of carrying around for almost a decade a really warm but fairly bulky sleeping bag (Marmot Never Summer 0F), I have decided to invest in a more compact one. _True to size (I am 6ft, lean & broad shoulders - medium fits perfectly - this bag is not roomy) _Good stitching (no down being released) _Warm (no cold spots - paired with an entry level bivy sack) _Ingenious SynergyLink connectors (I tend to toss around a lot and inevitably fall from my sleeping pad - this system prevented that and helped me in being well-rested) _Extremely compact + good quality compression sack _Warmth/Size ratio is excellent


_Would have bought a 0F version if it had been made available by Thermarest (to have a true 4 seasons sleeping bag)

Donald C.


Light and Warm


Very light and packable. Lofts up nicely(although it does take some time to loft up after being fully compressed) and is very warm for the weight. Temperature rating seems about right. I used this with temps in the low to mid 30s with a wool baselayer and socks and a down jacket. It was paired with an xtherm max pad and I was comfortable. My only issue is my feet were just warm enough, but that is not from the bag but that I am just over 6'6"(just above the recommended height for the bag) so my feet tend to compress the down in the footbox when I stretch out. It is a snug fit, but not overly tight, so it warms up quickly. The pad straps are probably helpful (I haven't used them) to keep everything in place. Otherwise, when you roll, and the bag comes with you, you will realize how much less down is on the bottom of the bag. I found it was noticibly cooler when I rolled on my side and my back only had the bottom insulation.


While the half-length, lightweight zipper by itself isn't a problem, paired with how snug this bag is does make it rather difficult to zip all the way up. Not a dislike, but for people who like a roomy bag, this is not it. You don't really get into it, but more put it on.

Daniel F.


Insanely light weight for the warmth!


Wait weight to warmth ratio! Packs down super small. And even has a strap to keep you on your pad! This is the kind of thing you see from small garage gear companies, nice to see it done from the best.


I have broad shoulders and the bag is definitely very snug , also the compression sack is a little too small, it's really hard to get sleeping bag into it to then compress it. I wish they would start using dry bags.