Sea to Summits lightest sleeping bag to date. A stripped down design for fast light 2-season adventures. The Spark Series sleeping bag delivers Sea to Summits trademark performance with their lightest ever design. The Spark 1 specially designed for minimalist outdoor adventures such as ultramarathons, adventure racing, ultralight trekking, climbing expeditions, and cycle touring. Everything about the Spark has been engineered to deliver optimum warmth without the weight penalty. A close-fitting mummy shape and ultra lightweight 10D nylon shell deliver a low bulk sleeping bag with a compact design and ultralight weight of just 348g.Ultra-Dry Down 850 insulation gives you a highly compressible premium goose down with water-repellent treatment that protects from both external moisture and internal condensation. This helps retain over 60 more loft and absorb 30 less moisture when compared with untreated down and continues to insulate even in damp conditions.The form-fitting design uses a 5545 fill ratio to insulate your core as the bag rotates with you throughout the night. A soft touch 15D nylon lining fabric features a down-proof, highly breathable construction to ensure a comfortable nights sleep. A 12 length YKK 3 zip sheds excess weight while the contoured, adjustable hood and tapered footbox round out the design. The Spark Series 1 sleeping bag from Sea to Summit for the fast moving outdoor adventurer looking for a balance of weight, size and thermal performance.