CWM MemBrain

The CWM is rated for -40°F (-40°C). It is designed specifically for high-altitude mountaineering and extreme cold, so it is overkill for standard three-season camping.

MemBrain is Marmot's proprietary waterproof, breathable fabric. It excels at shedding spindrift and preventing condensation from soaking the down insulation, which is critical when you are sleeping in a tent or snow cave for multiple days.

Yes, it uses 800-fill-power goose down treated with Down Defender. This treatment helps the down maintain its loft and insulation properties even if it gets slightly damp from body moisture or humid conditions.

The regular size weighs approximately 3 pounds 13 ounces. While it is impressively light for a -40°F bag, it is still quite bulky and will take up a significant portion of your expedition pack.

The hood features a multi-baffle design with a down-filled draft tube that seals tightly around your face. It is specifically engineered to prevent heat loss, which is the most common failure point in extreme cold bags.

You can, but it will likely be too warm unless you are camping in sub-zero temperatures. If you are typically camping in temperatures above 0°F, you will find this bag uncomfortably hot and unnecessarily heavy.