Sea to Summit Alpine APIII

The bag uses 850+ Loft ULTRA-DRY Down, which is treated to resist moisture and maintain its loft even if it gets damp. Combined with the water-resistant 3D NanoShell exterior, it is designed to keep you warm and dry in unpredictable alpine environments.

Yes, the Alpine APIII features expedition sizing, which is intentionally cut wider than a standard mummy bag. This extra room allows you to comfortably wear your base layers or down jacket inside the bag without compressing the insulation.

With a comfort rating of -20.2 degrees Fahrenheit, this bag is built for serious winter and high-altitude expeditions. It is specifically engineered to provide reliable thermal efficiency in severe, sub-zero conditions.

The Free-Flow zipper system includes a full-length main zipper and a half-length zipper on the opposite side. This allows you to open the bag for ventilation or fold the top down like a quilt if the temperature rises, giving you more control over your comfort.

Not at all. The bag features an anatomically shaped, oversized foot box designed to accommodate natural foot position and provide extra space, preventing your feet from compressing the down insulation at the bottom of the bag.

The Alpine APIII has a compressed volume of 30 liters. Given its high-loft insulation and expedition-grade warmth, it is relatively compact for a bag of this caliber, though it will still require a significant portion of your pack's capacity.