Synergy Sleeping Bag Liner is a sleeping sheet from Thermarest that provides comfort and warmth to the sleeping bag. Raises the comfort temperature by 3 ° C. Made of soft, stretchy polyester that absorbs sweat and oils that would otherwise be absorbed by the sleeping bag. Therm-a-Rest Synergy Sleeping Bag Liner Stargazer | Buy Therm-a-Rest Synergy Sleeping Bag Liner Stargazer here | Outnorth