We used 800-fill power on this down jacket because higher fill power works best for hikers, climbers and skiers who need mobility and warmth. With its impressive fill-count and a strategic box-wall construction, this is the warmest down jacket we’ve ever created, with the exception of the bespoke jackets we made for the Everest expedition team. Not only does the construction eliminate cold spots, we’ve added a down-filled collar and a shock-cord to keep cold wind out.