If you&';re forced to spend an unexpected night outdoors, stay warm with the SOL Emergency bivy. It reflects back up to 90% of your body heat, traps warm air and keeps out wind and water.The SOL Emergency Bivvy is a full-protection shelter that reflects 90% of body heat for warmth in extreme temperatures. The Emergency Bivy is made of a polyethylene material that is metalized to reflect back body heat.