Brennan 5406-P-06 Steel Pipe Fitting, External Hex Pipe Plug, 3/8-18 NPTF Male Head shape is hexagonal for increased leverage and use with a wrench Made from steel for strength Higher corrosion resistance than stainless steel 304 Male National Pipe Taper fine (NPTF) threads for a tight seal to female pipes Male threads for fitting into female fittings