Mountain Mafia sleeping bags are built utilizing 20d-400t DWR nylon. This DWR treated fabric was the obvious choice to provide a superior combination of durability, breathability, and light weight. Overfilled with 850+ fill power goose down our bags enjoy the extremely high insulation value to weight ratio that only goose down can provide. All bags incorporate full down draft collars and draft tubes along the length of the YKK zippers. This, along with draw strings and hook and loop fasteners work in concert to seal out cold drafts. Dual zipper sliders allow you to vent the foot box area effectively controlling your sleeping temperature.