This 6 in. x 4 in. Female Reducing Coupler is used to join 6 In Corrugated HDPE Pipe to 4 in. with a secure, snap-in connection. Makes a strong, leak resistant joint. HDPE material is strong, durable but lightweight. Compatible with polyethylene piping. Pipe lengths snap into the fitting to make a secure, leak resistant joint. HDPE material resists erosion and weather damage.