Westbrass D331-F-26 1-3/8-Inch NPSM Fine Thread Twist-and-Close Bath Drain Plug, Polished Chrome 1-3/8 in. NPSM twist & close style bath tub drain Fine thread drain shoe 1-3/8 in. NPSM (1-5/8 in. - 16 UNC) exterior Twist and lower to close and restrict draining water Heavy duty metal construction 1-3/8   in. NPSM twist &amp; close style bath tub drain Fine   thread drain shoe 1-3/8   in. NPSM (1-5/8 in. - 16 UNC) exterior Twist   and lower to close and restrict draining water Heavy   duty metal construction Do not use plumber&#039;s putty for installation use silicone seal