Make a leak-resistant connection between pipes using the Flexible Elastomeric PVC Coupling for 4 in. Concrete Pipe X 4 in. Cast Iron/Plastic Pipe. This easy-fit coupling has one end that slides onto 4 in. concrete pipe and one end that slides onto 4 in. cast iron or plastic pipe. Clamps on each end of the coupling tighten to secure it in place. Flexible coupling provides a rust-, chemical-, and corrosion-resistant connection that flexes with normal earth movement. Durable coupling is made of flexible elastomeric polyvinyl chloride. Clamp is made from series 300 stainless steel. Product is ICC, CSA, and IAPMO listed.