5/16" thick with two outer layers of aluminum foil. Each foil layer is bonded to a tough layer of polyethylene for strength up to 97% of radiant heat with an R-value up to 14.3 depending on application. Excellent vapor barrier for below grade. Can be used for radiant floors, crawl spaces, duct insulation, metal buildings, basement walls & attics. Square edge roll double bubble foil both sides 5/16" thick with two outer layers of aluminum foil Each foil layer is bonded to a tough layer of polyethylene for strength up to 97% of radiant heat with an R-value up to 14.3 depending on application Excellent vapor barrier for below grade Can be used for radiant floors, crawl spaces, duct insulation, metal buildings, basement walls & attics. Easy applied with tape & staples. Specifications Size: 24" x 10.