Twist & Close 1-1/2 in. NPSM Coarse Thread Bath Drain• 1-1/2 in. NPSM twist & close style bath tub drain• Coarse thread• 1-1/2 in. NPSM (1-7/8 in. - 11-1/2 UNC) exterior• Twist and lower to close and restrict draining water• Heavy duty metal construction• Do not use plumber"s putty for installation