Sea to Summit Spark Ultralight -9 Down Sleeping Bag

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The Spark Ultralight -9 Down Sleeping Bag is a mummy-shaped bag with a no-frill design for efficient insulation and minimal bulk on your lightweight cold-weather adventures. It combines ULTRA-DRY 850+ loft goose down with a soft 10D nylon shell and lining that compresses down small in the included compression sack for easy packing. It also comes with a storage cell.


  • 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; PFC-free DWR (durable water repellent) treatment keeps the hood and footbox highly water resistant
  • 850+ Fill Power, RDS-certified, Goose Down with ULTRA-DRY Down treatment for improved water resistance in damp conditions
  • 3/4-length #5 zip with anti-snag zip plow and two sliders
  • Vertical chest baffles, horizontal baffles in the lower half and base, box wall baffle construction throughout
  • Technical fitted hood with soft touch adjustment, extra deep for cosy-like feel
  • Standard front draft collar
  • Single, down-filled, draft tube along the top of zips
  • 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
  • Ultralight does not mean ultra-tight: The Spark mummy sleeping bags are snug but still have adequate wiggle room for the performance-oriented, backcountry user


Fits to 185cm (Regular), 198cm (Long)
Shoulder Width 77.5cm (Regular), 82.5cm (Long)
Foot Width 51cm (Regular), 56cm (Long)
Compression 13 Litres (both sizes)
Fill ULTRA-DRY Goose Down 850+ Loft, RDS certified
Fill Weight 480g (Regular), 540g (Long)
Average Weight 730g (Regular), 786g (Long)
Outer Material 10D nylon
Inner Material 10D nylon with a non-PFC DWR finish
Temperature Rating minus 2°C comfort rating woman / minus 9°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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