The US military Woodland M81 bivy cover is a waterproof and wind-resistant outer layer designed to protect sleeping bags in the field. It is part of the Modular Sleep System and can also be used as a stand-alone bivy sack.

• Pattern: Woodland M81 camouflage
• Material: Waterproof, breathable laminate fabric
• Compatibility: Modular Sleep System (MSS) components
• Function: Provides weather protection for patrol and intermediate sleeping bags

Issued to U.S. military personnel as the outer shell of the Modular Sleep System during the woodland camouflage era.