Genuine US military issue Modular Sleep System (MSS).
Genuine US Army and Marine Corps standard issue MSS consists of four components for sleeping in up to -30 F temperatures:
Goretex BIVY outer cover bag 60 F (1.5 lbs)
Patrol Sleeping Bag 30 to 50 F (3 lbs)
Intermediate Cold Weather Sleeping Bbag 30 to -10 F (4 lbs)
Compression Stuff Sack
Modular layering design.
Completely integrated system rated to -30 F when the user wears the expedition weight polypropylene shirt, drawers and issue cushion sole woolen socks. To obtain lower ratings, additional layers of Extreme Cold Weather Clothing articles are required.
Warmest system rated to 60 F with Goretex bivy cover as main bag and other bags as cushioning.
To obtain lower temperature ratings, additional layers of Extreme Cold Weather Clothing articles must be added to the user's clothing ensemble inside the sleeping bag.