Ultra-light and technical, the Sea to Summit Spark™ Series bags are designed to keep you as warm as possible while minimising packed weight and size.The Spark™ Series spans everything from an ultralight liner to an expedition weight mid-winter bag. While the end usage is very different, they reflect a design ethos of matching weather conditions to the lightest bag possible.The secret to the impressive performance is a combination of premium materials and careful design. The RDS 850+ Loft premium goose down, light-gauge #3 YKK zip and high performance 10D Nylon shell and 7D lining fabrics, set the stage for superior performance. These materials are combined with a contoured mummy design for efficient insulation, and that mummy design is then tweaked for each model to best fit the use scenario.ULTRA-DRY Down™ water-repellent treatment protects the down from external moisture and condensation from the inside of the bag, virtually eliminating the negative effects moisture has on down. All Sea to Summit Down Sleeping Bags use Responsible Down Standard (RDS) certified down. The ULTRADRY Down™ protection also makes the Spark™ an impressive hard-alpine or adventure racing bag, where every gram is counted and down has never been a viable option.  Features Ultralight 7D and 10D fabrics for minimal weight and packed sizeRDS 850+ Loft Premium Goose ULTRA-DRY Down™ for maximum insulation value Contoured mummy shape for comfort and efficient insulation Vertical chest baffles prevent down migration and cold spots Vertical box baffles in the torso area accommodates extra down and boosts warmth around the core, vertical baffles on chest optimises positions of down to prevent it moving during use Lower part of the bag uses a sewn through horizontal baffle construction to minimise weight ½ zip with two sliders aids access and allows ventilation from mid-section of bag Draft tube prevents heat loss through the zipper Includes hood draft collar Includes lightweight Ultra-Sil™ Nano compression bag for compact storage Materials: Shell: 100% Nylon, Lining: 100% Nylon, Primary Filling Material: GOOSE DOWN (Min. 90% Down), Stuffsack: 100% Nylon excluding Trims Sea to Summit Spark II SP2 -2°C Ultra Light Down Sleeping Bag - Long