Reflectix BP24050 24-Inch-by-50-Foot Bubble Pack Insulation Reflective insulation for use in a crawl space, attic, wall, metal buildings, and post and frame structures Fiber free, environmentally safe, easy to install, and lightweight Made up of seven layers, two outer layers of aluminum foil reflect most of the heat which hits them Each layer of foil is bonded to a tough layer of polyethylene for strength Two inner layers of bubble pack resist heat flow, while a center layer of polyethylene gives additional strength, 24" x 50' roll