MegaSleep Duo is a supremely versatile 4-in-1 sleep solution, offering multiple configurations and temperature ratings. It covers couples and solo sleeping with warm and cool night options. Simply flip the bag over to change the amount of insulation on the top side - dark blue side up for cool nights light blue side up for warm nights Also, each side can be converted into a solo bag or blanket, creating one for cool nights and one for warm nights. The MegaSleep is designed to fit perfectly on a MegaMat and MegaMat DUO. With its lightweight synthetic fiber filling, the thermal performance is sufficient for a cooler summer night. Furthermore, the smart zipper draft tube prevents cold spots. Depending on the insulation needs, the sleeping bag can be turned - dark blue side up for cool nights, light blue side up for warm nights. The wraparound zipper allows this sleeping bag to be quickly and easily converted into a blanket. Shell as well as liner material are PFC-free.