Why are there different NSN Options? Over the years, different government contractors have produced these items under different NSN numbers. Rest assured these are all the exact same product, they just have different part numbers. The 4-Part Modular Sleep System (MSS) sleeping bags and other components are constructed to be used in conjunction with each other, or separately to complete an interoperable system known as the extreme cold weather sleeping bag. The MSS is designed to provide comfort in temperatures ranging from 50°F to -50°F when wearing various layers of extreme cold weather clothing. The Waterproof Bivy Cover is produced utilizing waterproof, moisture-vapor-permeable material with all seams heat sealed. The Compression Stuff Sack is constructed with water resistant materials with adequate volume for both bags as well as the Bivy cover. This unique sack compresses the system to one cubic foot. Camo Green Patrol Bag. Woodland Camouflage Waterproof Bivy Cover. Weight: Approximately 9.8 lbs. The item “NEW USGI Modular Sleep System (MSS) 4-Piece Sleeping Bag Kit Bivy Cover Woodland” is in sale since Tuesday, November 5, 2019. This item is in the category “Sporting Goods\Outdoor Sports\Camping & Hiking\Outdoor Sleeping Gear\Sleeping Bags”. The seller is “legitkit” and is located in Virginia Beach, Virginia. This item can be shipped worldwide.