One roll of HD Butyl Rubber backed Aluminum Foil Tape 47 mils thickness. 6" x 50' Highly tacky butyl rubber backing makes a tight waterproof seal Popularly used for sealing roof flashing as well as making repairs in punctures in trailers, truck bodies, containers, RV's and campers This listing is per one roll of butyl rubber backed aluminum foil tape. 47 mils thickness. Popularly used for sealing roof flashing as well as making repairs in punctures in trailers, truck bodies, containers, RV's and campers. Great for sound-proofing vehicles too! Highly tacky butyl rubber backing makes a tight waterproof seal.