Sea to Summit Spark Pro Ultralight -1 Down Sleeping Bag

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Lightweight and functional, the Spark Pro Ultralight -1 Down Sleeping Bag is optimised for comfort and versatility on lightweight adventures. It combines ULTRA-DRY 950+ loft goose down with soft 10D nylon, a mummy shape for efficient insulation and minimal bulk with a Free Flow Zip System for maximum ventilation and the ability to open it out as a quilt. It comes with a compression stuff sack for compact packing.


  • Mummy Fit: Fitted cut with generous anatomical footbox and technical hood, to maximise thermal efficiency and minimise bulk and weight
  • bluesign®-approved 10D nylon shell and lining fabric offers breathability, protection and effective temperature regulation for premium comfort in the outdoors
  • 10D nylon's waterproof and breathable features offer added protection and prevents exposure to tent wall condensation
  • 950+ Fill Power, RDS-certified, Goose Down with ULTRA-DRY Down treatment for improved water resistance in damp conditions
  • Free Flow Zip System for reliable, snag-free operation and minimal weight:
    • Primary zip: full-length #5 with zip-plow and two sliders
    • Secondary zip: 1/4-length #3 with zip-plow and two sliders
    • Footbox zip: #3 with two sliders
  • Hybrid box baffles with vertical chest baffles, horizontal baffles in the lower half and base, box wall baffles at the top half of the bag and sewn through quilted construction in the lower half
  • Technical fitted hood with soft touch adjustment, extra deep for cosy-like feel
  • Fitted front draft collar: scalloped over the neck and oversized at the shoulders
  • Pairs with women's Sea to Summit bags and the QuiltLock System allows integration with Sea to Summit quilts
  • Comes with an Ultra-Sil compression bag and a storage cell


Fits to 185cm (Regular), 198cm (Long)
Shoulder Width 77.5cm (Regular), 82.5cm (Long)
Foot Width 51cm (Regular), 56cm (Long)
Compression 8 Litres (both sizes)
Fill ULTRA-DRY Goose Down 950+ Loft, RDS certified
Fill Weight 310g (Regular), 365g (Long)
Average Weight 619g (Regular), 672g (Long)
Outer Material 10D nylon
Inner Material 10D nylon with a non-PFC DWR finish
Temperature Rating 3°C comfort rating woman / minus 1°C Lower comfort rating for men; Temperature rated in accordance with ISO 23537-1:2022

ULTRA-DRY Down™: With the introduction of water-repellent ULTRA-DRY Down™ Seat to Summit have virtually eliminated the negative effects moisture has on down. The ULTRA-DRY Down™ water-repellent treatment protects the down from external moisture and condensation from inside the bag. It is a permanent (no loss of treatment effect has been seen in over 14 wash cycles) Nano-level water repellent polymer treatment applied to Sea to Summit high loft, high quality down. The Nano-thin treatment vastly improves the down's reaction to water without effecting its weight or loft performance. ULTRA-DRY Down™ retains over 60% more loft and absorbs 30% less moisture when compared with untreated down. Sea to Summit sleeping bags dry out 60% faster than bags with untreated down. The Nano-level treatment also inhibits bacterial and microbial growth, which makes Sea to Summit sleeping bags more hygienic and improves their lifespan.

Responsible Down Standard (RDS): The RDS is helping to shift the entire down and feather industry towards more humane animal rearing and handling practices. Overseen by the industry leading Textile Exchange, the RDS requires independent, third party assessments of all aspects of animal rearing and handling throughout the entire supply chain. By only using down that meets the audited requirements of the RDS we can have confidence that each phase of the collection process has been completed with the welfare and ethical treatment of waterfowl in mind. To find out more about how the RDS is improving animal welfare during down collection, please visit (link will open a new window).


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