Nashua 360-17/SI3100 Polyken 360-17 Heavy Duty Foil/Butyl Rubber Tape, 17 mil Thick, 100' Length x 3" Width, Aluminum, Silver Core: 3 inch diameter Backing/carrier: 2 mil aluminum foil - printed Adhesive: butyl rubber Release liner: low density polyethylene (ldpe) film Thickness: 17 mils (carrier, adhesive) 15 mils (adhesive) 2 mils (carrier)