REI Co-op Magma Sleeping Bag

The '15' in the name refers to the EN/ISO comfort rating of 15°F, which is the temperature at which a standard user should feel comfortable sleeping. Keep in mind that individual metabolism and pad insulation play a huge role, so if you are a cold sleeper, you might want to pair this with a high-R-value sleeping pad.

Yes, the Magma 15 uses 850-fill-power goose down that has been treated with a water-repellent finish. While this helps the down retain its loft if it gets slightly damp, it is not waterproof, so you should still use a dry bag or pack liner to keep it protected during heavy rain.

The Magma 15 features a slightly more contoured, athletic cut than a traditional rectangular bag to maximize thermal efficiency. It is designed to be snug enough to minimize dead air space you have to heat up, but it still offers enough room for most people to shift positions comfortably.

The Magma 15 is designed as a standalone technical bag and does not feature a universal zipper system for connecting to other models. If you are looking to share warmth, you would be better off looking for bags specifically designed with compatible left- and right-hand zippers.

To preserve the loft and longevity of the down, you should store the bag uncompressed in the included large cotton storage sack or hang it in a closet. Keeping it compressed in its stuff sack for long periods will eventually damage the down clusters and reduce the bag's warmth.