This entire line of bivies weigh significantly lighter than their predecessors, and feature a smaller footprint that saves on pack space and weight for convenience, comfort, and effectiveness. Our ultimate goal was to create shelters that weigh less than a single person tent, and the result is a streamlined collection of bivies ideal for thru-hikers, bikepackers, and fastpackers looking to shed ounces and maximize performance.

Browse our bivy sack guide below to find out which features, technologies, and shelter choice is right for you.

Interstellar Bivy

Four-season waterproof, durable, and versatile bivy choice for adventurers looking for a little something extra out of their shelter.

• Fabric: AscentShell™
• Weight: 21 oz. with pole, 19.2 oz without pole
• Size: 82” length x 26” top width x 17” top height
• Best for: Expedition and Extreme Conditions
• Why you’ll love it:
  • Shares the same name as the Interstellar Jacket, Outside Magazine’s Gear of the Year award winner for its supremely breathable and waterproof AscentShell™ technology.
  • Newly designed side entry makes getting in and out of your shelter faster and easier, without any butt-to-ground contact.
  • TPU laminated bivy floor has a bathtub construction that protects you from ground water and rain spray. The fabric’s 40D ripstop also prevents rips and tears.
  • Removable single pole can add headspace or be left behind to save weight.
  • Two stake loops to secure shelter down in high wind.
  • Innovative zipper system uses 6 zipper sliders on mesh and shell to free arms and face, letting you wear your shelter like a jacket for the ability to cook, clean, read, and more – right from the comfort of bed.
  • Sombrero-style crown provides larger headspace and gear storage.

Stargazer Bivy

The easiest bivy choice for alpinists, backpackers, and campers who prefer a room (or shelter) with a view.

• Fabric: AscentShell™
• Weight: 19.2oz with pole, 17.2oz without pole
• Size: 82” length x 26” top width x 20” top height
• Best for: Fast and Light
• Why you’ll love it:
  • Seam-taped, breathable, and waterproof AscentShell™ technology ensures you’ll stay safe from the elements, without compromising breathability.
  • Newly designed side entry makes getting in and out of your shelter faster and easier, without any butt-to-ground contact.
  • TPU laminated bivy floor has a bathtub construction that protects you from ground water and rain spray. The fabric’s 40D ripstop also prevents rips and tears.
  • Removable single pole can add headspace or be left behind to save weight.
  • Two stake loops to secure shelter down in high wind.
  • Enlarged head space and mesh screen to keep out bugs and allow for optimum stargazing.

Alpine Bivy

GORE-TEX waterproof power for winter mountain missions.

• Fabric: GORE-TEX Respiration Positive
• Weight: 20.6oz with pole, 18.7oz without pole
• Size: 82” length x 26” top width x 19.75” top height
• Best for: Expedition and Extreme Conditions
• Why you’ll love it:
  • Seam-taped waterproof GORE-TEX Respiration Positive eliminates interior condensation before it has a chance to build up.
  • TPU laminated bivy floor has a bathtub construction that protects you from ground water and rain spray. The fabric’s 40D ripstop also prevents rips and tears.
  • Traditional clamshell opening lets you breathe freely without letting in weather.
  • Removable single pole can add headspace or be left behind to save weight.
  • Two stake loops to secure shelter down in high wind.
  • New Fly Fastener stores shell fabric away from face, and is easily deployed in the event of an unexpected chill or sudden rain.
  • Updated pole positioning keeps bivy erect for ample headroom.
  • Reduced mesh fabric ensures a more taut bug barrier that won’t sag.   

Helium Bivy

Award-winning for its ultralight prowess, made even lighter.

• Fabric: Pertex® Shield+
• Weight: 16.2oz with pole, 14.3oz without pole
• Size: 82” length x 26” top width x 19.75” top height
• Best for: Fast and Light
• Why you’ll love it:
  • 14% lighter than last season’s Helium Bivy.
  • Seam-taped waterproof Pertex® Shield+.
  • Traditional clamshell opening lets you breathe freely without letting in weather.
  • TPU laminated bivy floor has a bathtub construction that protects you from ground water and rain spray. The fabric’s 40D ripstop also prevents rips and tears.
  • Removable single pole can add headspace or be left behind to save weight.
  • Two stake loops to secure shelter down in high wind.
  • New Fly Fastener stores shell fabric away from face, and is easily deployed in the event of an unexpected chill or sudden rain.
  • Updated pole positioning keeps bivy erect for ample headroom.
  • Reduced mesh fabric ensures a more taut bug barrier that won’t sag. 

Helium Emergency Bivy

Under 10 oz. of adventure insurance that packs down to the size of a beer can.

• Fabric: Pertex® Shield
• Weight: 9.6 oz.
• Size: 84” length x 36” top width
• Best for: Emergency
• Why you’ll love it:
  • The lightest weight and smallest packed size we offer in a bivy, the perfect emergency shelter for your 10 Essentials kit.
  • Reusable design and durable material means your investment isn’t wasted after a single use.
  • Seam-taped waterproof Pertex® Shield+.
  • Tube construction with cinch closure to seal out the elements.

Browse All Bivy Sacks.

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Photos by Elise Giordano.