This Therm-a-Rest Mattress vs Cheap Pads - Thermarest MondoKing 3D Air Mattress
TheOutdoorGearReview
Expert Pick #08
Therm-a-Rest Hyperion 20.
Nikwax Hydrophobic Down in a 1 lb 5 oz mummy bag rated to 20°F. The ultralight pick for backpackers who want a bag, not a quilt.
The Verdict.
8.6/ 10
Gavler Meta-Score
“The lightest 20°F mummy bag in production. Nikwax Hydrophobic Down provides genuine moisture insurance. Right pick for UL backpackers who want a traditional bag shape at quilt-competitive weights.”
The Gavler Verdict
Where to Buy.
Prices checked regularly
Best price$339.95
90-day price history
Price History
Steady at $340 for the entire 90-day tracking window — no increases, no discounts, across 74 tracked days.
Tracked daily across retailers. Vote Want itabove and we’ll alert you the moment the price drops.
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Precision Engineering
1 lb 5 oz
Lightest 20°F mummy bag in production — quilt-competitive weight.
Nikwax Hydrophobic Down
Permanent DWR treatment on individual clusters retains 90%+ loft when damp.
ThermaCapture Lining
Reflective interior lining adds warmth without insulation weight.
Technical Specifications
Temperature Rating20°F / -7°C
Fill900-fill Nikwax Hydrophobic Down
Weight1 lb 5 oz (595 g)
Shell7D/10D ripstop nylon
ShapeMummy
The Scoreboard
Expert Consensus85%
Community Rating84%
Best-in-class for mummy-bag loyalists. Snug fit limits the appeal for side-sleepers.
Cast Your Vote
Do you think Therm-a-Rest Hyperion 20 deserves the #8 spot in Best Backpacking Sleeping Bags?
Global Critique
“Lightest credible 20°F mummy bag on the market. The Nikwax treatment is the real deal.”
Outdoor Gear Lab
“The mummy bag for ultralight backpackers who haven't converted to quilts.”
Backpacker Magazine
“ThermaCapture lining adds perceptible warmth without weight — a genuine engineering advantage.”
Section Hiker
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