The Sea To Summit Trek Sleeping Bag gives us room to stretch out in the back of our trusty adventure-mobile or while we gaze at the stars through our tent canopy. The warm and lofty 650-fill duck down is treated with a water-resistant Ultra Dry treatment to keep us cozy in damp conditions, with a DWR treatment on the soft polyester fabric for double the protection. The semi-rectangular shape gives us plenty of room in the footbox and shoulders and allows us to sleep in natural positions. The Free Flow Zip Technology ensures incredible ventilation, allowing us to completely customize the level of warmth so we stay comfortable on warm summer nights.