Fully-galvanized 1.25 inch washers with tabs And rust-free 1 5/8 inch screws for securing HYDROBLOK wallboard and accessories. Specialty screw head allows for use with either #2 Phillips or #2 Robertson screwdriver bits. Washers must be secured with HYDROBLOK Wallboard screws. HYDROBLOK Wallboard Washers and Screws are also available individually in 1000 pc buckets.