Sea to Summit's Flame range of sleeping bags has been specifically designed for women to provide high comfort and light performance for a demanding range of applications. All Flame sleeping bags are characterized by their ultra-light weight and minimal packing size as well as an excellent thermal performance. The Flame FmIV's fully sewn vertical boxing chambers contain an extra amount of down to reduce cold bridges. The expedition size ensures extra space for additional layers of clothing. The vertical chambers in the chest area optimise the distribution of the down and prevent it from slipping. A full-sided zipper with two sliders allows easy access and variable ventilation. A zipper channel, a hood and a heat collar also prevent heat loss. Ultra Dry DownUltraDry Down is a PFC-free water-repellant treatment applied to the down used in all Sea to Summit sleeping bags. UltraDry Down retains over 60 % more loft, absorbs 30 % less moisture and dries out 60 % faster when compared to untreated down – which means the down will insulate better even in damp conditions. The treatment also inhibits bacterial growth, making your bag last longer. UltraDry Down treatment is an environmentally friendly application.