Connect lengths of 4 in., single-wall, corrugated polyethylene drainage pipe with the Advanced Drainage Systems 4 in. Polyethylene Internal Coupler. The coupler's polyethylene material resist corrosion and abrasions. Made from high-density polyethylene so it's strong and durable. Use to connect lengths of 4 in., single-wall, corrugated polyethylene drainage pipe. 1-piece molded design makes a secure, leak resistant joint. Snaps easily into pipe.