Sea to Summit Ascent AcIII 0 Sleeping Bag

$499.00to $519.00
Color: Spruce/Moss
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Shipping restrictions apply.

Light, warm and comfortable, the versatile Sea to Summit Ascent AcIII 0 sleeping bag is surprisingly roomy for a mummy bag, while still providing the thermal efficiency you need above the treeline.


  • Tapered rectangular shape creates the perfect balance of space and adaptable warmth
  • 750-fill-power UltraDry Down™ certified to the Responsible Down Standard (RDS)
  • Anatomically shaped footbox retains warmth around your feet
  • Vertical chest baffles prevent down migration and cold spots
  • Generously sized hood with dual cord adjustment offers maximum warmth retention
  • Lightweight 20-denier nylon shell and lining fabrics offer a minimal packed size and maximum breathability
  • Free-Flow half-zip on the right side; full-length, 2-way #5 YKK zip left side and separate foot zips allow maximum ventilation and use as a quilt
  • Includes Ultra-Sil™ compression bag for compact storage
  • Oversize draft tube with antisnag materials
  • Oversize neck draft tube with dual adjustment system
  • Large internal security pocket
  • This bag is designed to easily zip with another (second sleeping bag not included)


Many sleeping bags are rated for temperature by an independent testing protocol. REI and the broader industry now use the International Organization for Standardization (ISO) 23537 protocol, which improves on the older European Norm (EN) 13537 standard; you may still see older items in our assortment that were only EN tested. With either protocol, each bag gets a Comfort (or T-Comfort) rating and Lower Limit (or T-Limit) rating. The Comfort rating is the lowest temperature at which the bag will keep the average "cold sleeper" comfortable, and the Lower Limit rating is the lowest temperature at which the bag will keep the average "warm sleeper" comfortable. Ratings are based on a person wearing one long underwear layer and a pair of socks, sleeping on an insulated surface with a minimum R-value of 5.38. Many brands use the Comfort rating for women's bags and the Lower Limit rating for men's and unisex bags. Everyone's body and sleep comfort differ, and conditions of use (posture, clothing, sleeping pad R-value, wind, humidity, etc.) affect total insulation, so EN and ISO ratings are intended as a guideline to help you compare products, rather than a guarantee of warmth.
View all Sea to Summit Backpacking Sleeping Bags

Technical Specs

Best Use


Tested Lower Limit

0 degrees (F) - EN

Tested Comfort

15 degrees (F) - EN

Temperature Rating (F)

0 degrees (F)

Temperature Rating (C)

-10 degrees (C)


Regular: 2 lbs. 15 oz.

Long: 3 lbs. 3 oz.


20-denier nylon

Zipper Location


Insulation Type


Water-Resistant Down



750-fill-power UltraDry Down

Fill Weight

Regular: 1 lb. 10 oz.

Long: 1 lb. 14 oz.


20-denier nylon

Sleeping Bag Shape


Fits Up To (in.)

Regular: 72 inches

Long: 76 inches

Shoulder Girth (in.)

Regular: 61 inches

Long: 65 inches

Hip Girth (in.)

Regular: 57 inches

Long: 61 inches

Stuff Sack Size


Stuff Sack Volume


Compressed Volume





Down certified to the Responsible Down Standard (RDS)

56 reviews with an average rating of 4.6 out of 5 stars

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