Both the shell & liner (unless flannel lined) are made with our super-light water/wind resistant nylon. Oversized draft tubes add total protection against cold air coming in or heat leaking out. Ergonomic Hood designed to wrap around your head for comfort & prevent heat loss. Hyperloft Microfibre fill,super loft-super warm even when wet!! YKK zipper: Your bag comes with the best zipper out there and it's double stiched for extra strength! Overlapping double layer construction,that gives you ultimate heat retention and prevents cold spots from forming with our 2 layer construction.. Wider means better: Wider chest & shoulder designed bag to let you sleep in style... Black Pine bags are designed for total comfort and incredible warmth. ALL Black Pine bags are filled with Hyperloft Microfibre fill.