UM68B,UM70B Crimped blue plastic fill, staple set in a wax tumbled hardwood block. Chemical and water-resistant fiber 1-3/4” trim, block size is 8” or 20” long x 3” wide. Available in long or short handle. AST8TH 9” x 2-3/4” synthetic block with one threaded hole and one tapered hole. Vinyl bumper encircles block. Flagged synthetic fill, 2-1/2” trim. Fountain style. This brush does not take a set, last longer than all others we have tested and hold a volume of water. Perfect for highly polished surfaces, windows and wall washing.