We used 800-fill power because higher fill power jackets perform for athletes like hikers, climbers, and skiers who need lightweight down jackets for 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 the cold out.