If every gram counts and you prefer to sleep as a duo, the Sea to Summit Spark -9°C Double is probably the right sleeping bag for you. This two person Spark is filled with RDS-certified 850+ fill power goose down that has been PFC-free treated with Ultra-Dry Down and is equipped with a technical hood and zip cover to retain warmth. A super-breathable 10-denier nylon inner material ensures comfort, while the 10D outer material with a PFC-free DWR coating and a highly water-repellent hood and foot box block wind and condensation.