The Sea to Summit Spark Pro Ultralight Down Sleeping Bag is a technical down bag, engineered for warmth at the lightest weight and smallest compressed size. Ideal for backpacking, bike packing, and touring, the mummy style keeps the cold out and the warmth in. Our highest-loft, 950 fill power goose down insulation (Responsible Down Standard certified) is treated with proprietary non-PFC Ultra-Dry Down treatment to improve reaction to moisture and retain loft and performance in rugged conditions. The contoured mummy shape provides adequate room for a natural sleeping position. Front draft collar is fitted around the neck and oversized at the shoulders to retain warmth. The ultralight 10D nylon shell is treated with PFC-free DWR and offers cutting-edge packability and warmth. The 10D liner fabric allows the bag to breathe and remain comfortable. A YKK #5 zipper operates snag-free. The Free Flow Zip system ensures maximum ventilation and the flexibility to open the bag flat as a quilt. The Sea to Summit Spark Pro Ultralight Down Sleeping Bag is available in two sizes: Regular (max user height of six feet) and Long (max user height of six feet six inches); and two temperature ratings: 30-degree and 15-degree. Baffle construction varies by temperature rating for each specific use: the 30-degree model employs hybrid box baffles in torso for warmth and sewn through baffles in the leg area to reduce weight; the 15-degree model uses full box baffles for maximum warmth. It includes an Ultra-Sil compression sack and storage cube. Sea to Summit products are guaranteed against defects in materials or workmanship for the lifetime of the product.