This is a Genuine U.S. Army Modular Sleeping System . These are used/repaired but in good surplus condition overall and contain four parts. This is one of the best sleeping systems available and is constructed to insulate the user in environments ranging from mild weather to extreme cold weather.
When you nest the bags together inside the bivy cover the complete system is rated for -20º F (in sleeping clothes, this changes to -30º F wearing light insulation like a microfleece shirt and pants, and -50º F when wearing ECWCS clothing).
The whole system is 84” x 32" tapered, with a boxed foot that will accommodate boots and has twice the insulation as the rest of the bag! The hood adjusts for heat retention; includes nylon draw cord with barrel lock and sewn-in, quilted chest collar prevents air drafts up and down through the hood. The bags have zippers at both ends so you can easily ventilate. This system is also free from cold spots; the insulation does not migrate in the bag. This is versatile and will work in all environments.