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Sea to Summit Ascent AC I

Size: Regular

Be prepared for the unpredictable with Sea to Summit's adaptable Ascent™ Series bags. The Sea to Summit Ascent I is a unisex down sleeping bag that is light, warm, and comfortable, and designed to be surprisingly versatile for all adventures.

Light, warm, comfortable and most importantly, adaptable. Offering the perfect backpacking balance of comfort vs weight, S2S Ascent™ Series sleeping bags have more space than traditional mummy bags, yet still provides the thermal efficiency you need when exploring above the tree-line.

Free Flow Zip System

Strategically placed zips offer ventilation options and freedom of movement.
The Free-Flow zip design ensures your sleeping bag retains maximum warmth and efficiency when needed and multiple ventilation options when it’s not. The half zip on the right side of the bag (left side on women’s bags) provides freedom of movement for both arms, additional ventilation and also means the top third of the bag can be folded down as a mini quilt when the mercury climbs higher than expected. A separate foot zip on the Ascent, Altitude, Traverse and Venture provides extra ventilation and also transforms the bag into a full quilt.

750+ Loft
750+ Fill Power indicates that 1 oz of down will re-expand to over 750 cubic inches after compression. Higher loft means that less down can be used to achieve the same temperature rating – important for performance sleeping bags. The loft and down quality/composition are independently tested by the International Down and Feather Laboratory (IDFL) – a copy of the certification is supplied with every Sea to Summit sleeping bag.

ULTRA-DRY Down™ is a permanent nano-level water repellent polymer treatment applied to our down which protects it from external moisture and condensation from inside the bag virtually eliminating the negative effects moisture has on down.

More Help? For further assistance on choosing your down sleeping bag, we have an article explaining fill power, the pros and cons of down over synthetic insulation and more info on caring for your bag available to view here: A Guide to Down Sleeping Bags.



  • Tapered rectangular shape for perfect balance of space and adaptable warmth
  • Super-light 20D Nylon shell and lining fabrics for minimal packed size and maximum breathability
  • RDS 750+ Loft ULTRA-DRY Down™ for superior insulating power
  • Vertical chest baffles prevent down migration and cold spots
  • Free-Flow half right side, full length two-way #5 YKK left side and separate foot zips for freedom of movement, increased ventilation and dual-use as a quilt
  • Oversized draft tube with anti-snag materials, prevents heat loss through zipper
  • Oversized neck draft tube with a dual adjustment system for even cinching and maximum warmth
  • Generously sized hood and dual cord adjustment for maximum warmth retention
  • Anatomically shaped footbox allows maximum down lofting, minimising heat loss from your feet
  • Large internal pocket for GPS / phone / valuables
  • Includes Ultra-Sil™ Compression Bag for compact storage
  • Zip Coupling: This bag can be zipped to the Sea to Summit Women’s Altitude, Journey and Venture sleeping bags


  • Maximum body size: 183cm (Regular) | 198cm (Long)
  • Pack size: 40x18cm (Regular)
  • Comfort Temperature: 2 °C
  • Comfort Temperature limit: -4 °C
  • Extreme temperature limit: -21 °C
  • Insulated collar: Yes
  • Main Fabric: 20D Nylon
  • Filling: 330g (Regular) | 370g (Long)
  • Fill power 750 cuin

Weight: 860g (Regular) | 930g (Long)

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