The US Army modular sleeping bag system is among the best there is. This is the Gore-Tex bivvy bag, which means the outermost layer of the whole system. Modular sleeping bags are like layered clothing: you use different parts together to adjust for conditions.
Meant to fit for any environment or weather, the US Army modular sleeping bag system has it all. The modularity captures insulating layers of air between the bags as a bonus. For sleeping in the field without a proper shelter, a bivouac sack is necessary to prevent the sleeping bag(s) from getting wet.
As a side note, the innermost bag is the Intermediate bag, which alone offers a tolerable sleep in as cold as -10 degrees Celsius (14 F). The Patrol bag alone is a summer bag rated for +10 °C (50 F)and packs very small. Together the Intermediate and Patrol bag are good for -30 °C (-22 F), i.e., you will survive in it.
When additional protection is required, this Gore-tex bivvy covers the whole thing. It can be used with most other sleeping bags as well, as it is quite large. It offers good waterproofing capabilities and a little extra insulation while still letting moisture out.
Made to high-quality specs with genuine Gore-Tex material and taped seams. It can be machine washed with a synthetics program and a liquid detergent. Specific membrane-friendly stuff is recommended, as well as a waterproofing treatment. Low heat tumble dry helps the treatment.
Waterproof and breathable fabrics work better when cared for. Just avoid powder detergents and softeners; they will clog the membrane, loosen tapes and wash off your NIR protection.
Made in USA! Used but in good, serviceable condition.
Dan T.
Pete