Yellowstone ultra lite 150 mummy sleeping bag blueblack description the ultra lite 150 offers a bit more comfort than the ultra lite 100 subsequently this mummy shaped sleeping bag has a little more insulation which increases the chances of a good nights sleep it has an internal pocket to protect valuables and has been designed with a water resistant shell so that leaking rain water will run off of it if you want a sleeping bag that keeps you that little warmer and a little cosier