Eliminates all screws Eliminates need for separate overflow test plug Eliminates leaks due to loose overflow attachment Eliminates dual inventory of one and two-hole overflow plates 1-1/2 to 11-1/2 in NPSM (coarse thread) 1.865 in Dia (outside thread) 11.5 TPI Sturdy 1-1/2 in SCH 40 Stopper, knobs and bodies determined by tub closure that is lift and turn etc