The Spark SpI is the lightest sleeping bag Sea to Summit have made to date. Pared down to the bare necessities, the SpI is an adventure racer's dream. Featuring Ultra-Dry Down, 850+ Loft, 90/10 Premium Goose Down. The bag is a contoured mummy shape, with a 10D nylon shell for minimal weight and bulk. The bag comes with a lightweight Ultra-Sil compression bag and a combined storage cell/laundry bag.