NIBCO 4818 Series PVC DWV Pipe Fitting, Plug, 4" NPT Male Plug for closing the end of a pipe or fitting Male National Pipe Taper (NPT) threads for connecting to a female threaded pipe PVC-DWV for corrosion resistance, high strength, and less weight than fittings made from metal Smooth interior finish for reduced friction and material buildup Meets specifications ASTM D2665 and D3311 for quality assurance