Aquasol AFBT-2.5-200 Fiback Fiberglass Weld Backing Tape, 2.5” W x 82 ft L, 200 AmpAquasol AFBT 2. 5 200 Fiback is a fiberglass weld backing tape designed to help eliminate or reduce the need for back purging on open root welds by creating a backing enclosure on the underside of the joint. It uses an adhesive backed aluminum tape with a center woven fiberglass strip that supports the weld pool and helps produce a clean root profile on plate, sheet, and pipe welds. The fiberglass strip is rated up to 1,022F (550C) and the adhesive is