NIBCO 4803 Series PVC DWV Pipe Fitting, Adapter, 4" Hub x NPT Female Adapter for connecting pipes or fittings of different types Hub opening on one end and female National Pipe Taper (NPT) threads on the other for connecting two pipes with different ends 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