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. Deep threads are designed so spring washer slides on easy, yet can’t pull off. Nail is rigidly welded to collet. This item is sold in a 5 gross box (720 pcs. of each item).