Add versatility to your Western Mountaineering sleeping bag with the Summer or Three Season Bag Expander. Designed to zip into any mummy-style Western Mountaineering sleeping bag, the expander gives you more elbow room, or a little more snuggle room for you and a partner. Like all of our sleeping bags, these expanders are filled with premium quality 850-fill-power goose down for the highest warmth to weight ratio.

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).