Add versatility to your Western Mountaineering sleeping bag with the Three Season Bag Expander. Designed to zip into any mummy-style Western Mountaineering sleeping bag, the expander gives you more elbow room in summer, and more snuggle room for you and a partner when the temps drop in early spring and late fall. Western Mountaineering is all about high-quality down, so they stuffed this bag expander with the same 850-fill-power goose down found in their sleeping bags.

The Western Mountaineering sleeping bag expander works best with 6 foot bags, but will work with any length, with a bit of overlap (most of the length difference between the bags is below the zipper in the feet).

Note: The Bag Expander is designed for use only with Western Mountaineering bags. It may or may not work with other brands.

Like all of Western Mountaineering's sleeping bags, the Bag Expander is made by hand in San Jose, California. Their down is sourced from free-range mother geese who are never live-plucked or force-fed.