Ultra-light and technical, the Spark Series bags are designed to keep you as warm as possible while minimising packed weight and size. The Sp0 is ideal for mid-summer fast hikes or adventure racing. Sea to Summit's quilted construction minimizes weight and ensures that the down stays in place. The Spark Sp0 can also be used as a liner to improve the thermal performance of another sleeping bag. Ultra Dry DownUltraDry Down is a PFC-free water-repellant treatment applied to the down used in all Sea to Summit sleeping bags. UltraDry Down retains over 60 % more loft, absorbs 30 % less moisture and dries out 60 % faster when compared to untreated down – which means the down will insulate better even in damp conditions. The treatment also inhibits bacterial growth, making your bag last longer. UltraDry Down treatment is an environmentally friendly application.