This is a #30 button back with a 7/8" long threaded nail. When anchored with a spring lock washer, the treaded nail is a fast, positive alternative to prong tufting. Just insert the nail through the upholstered construction and fasten it on the back with a spring washer - Item #BMPNW sold separately. This item is sold in a 1 gross box (144 pcs. of each item).