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Therm-a-Rest Altair -18C Down Sleeping Bag

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The Altair sleeping bag is designed to provide efficient warmth down to 0F (-18C), while offering light, packable performance that makes each day in the mountains more enjoyable. Like all Therm-a-Rest sleeping bags, it integrates with your mattress to eliminate the sliding, twisting and cold spots that can interrupt sleep.

  • Sleep Securely: SynergyLink Connectors bring your sleeping bag and mattress together for uninterrupted sleep.
  • Sleep Warmer: Zoned Insulation puts fill where you need it most, for efficient warmth.
  • Move Freely: Our Efficient Comfort Fit design gives you room to move where you need it, without creating too much space to heat efficiently.
  • Carry Less: Lightweight, 750+ fill goose down offers compressible warmth.

Altair is the twelfth brightest star in the night sky, and is used in celestial navigation.


Draft Tubes & Collar, Snag Free Zipper, Stash Pocket, Sculptured Hood, Trapezoidal Footbox, Storage & Stuff Sack

Color Blue Blue
Weight 2 lbs 7 oz / 1120 g 2 lbs 10 oz / 1200 g
Fits 6 ft / 183 cm 6 ft 6 in / 198 cm
Girth, Shoulder 62 in / 158 cm 64 in / 163 cm
Girth, Hip 58 in / 147 cm 60 in / 152 cm
Girth, Foot box 40 in / 102 cm 40 in / 102 cm
Width 30 in / 76 cm 30 in / 76 cm
Length 75 in / 190 cm 84 in / 213 cm
Packed dimension 8 x 18 in / 15 Liters 8 x 18 in / 15 Liters
EN Comfort -5 C / 24 F -5 C / 24 F
EN Limit -11 C / 12 F -11 C / 12 F
EN Extreme -31 C / -23 F -31 C / -23 F
Fill 750+ Goose Down 750+ Goose Down
Fill weight 1 lb 4 oz / 580 g 1 lb 7 oz / 640 g
Liner fabric 30D Nylon 30D Nylon
Shell fabric 30D Nylon Ripstop with DWR 30D Nylon Ripstop with DWR
Zipper side Left Left
Country of Origin Made in China Made in China

Temperature Ratings

Therm-a-Rest sleeping bags are rated to both US and European Norm (EN 13537) standards. All ratings are developed from procedures and testing conducted by independent organizations in the US and Europe. Sleeping bags and blankets without hoods are not subjected to EN testing.

  • EN Comfort: At this temperature, a standard woman can sleep comfortably in a relaxed position.
  • EN Limit: The lowest temperature at which a standard man will be able to sleep comfortably through the night. This rating is relatively close to those commonly used in North America.
  • EN Extreme: At this temperature, a standard woman can survive for at least six hours.