Frost King E/O 3/8 in. Dia x 350 ft. Contractor Pack Caulk Backer Rod

The Thermwell Products 3/8 in. x 350 ft. Caulk Saver Contractor Pack helps insulate and cushion while reducing the amount of caulk needed to fill or seal large openings. Use to back fill large gaps before applying caulk (caulk sold separately). Helps insulate and cushion while reducing the amount of caulk needed to fill or seal large openings.