48" x 50', Standard Edge Double Bubble Foil Both Sides Reflective Insulation, 5/16" Thick With Two Outer Layers Of Aluminum Foil, Each Foil Layer Is Bonded To A Tough Layer Of Polyethylene For Strength, Reflects Up To 97% Of Radiant Heat, R-Value Up To To 14.3 Depnding Upon Application, Excellent Vapor Barrier For Below Grade, Can Be Used For Crawl Space, Duct Insulation, Side Walls, Metal Buildings, Basement Walls & Attics, Product Has Been Evaluated By ICBO, BOCA, CCMC, SBCCI & Dade County, Easy To Install With Tape & Staples.