Couplers are one of the most simple and inexpensive types of PVC fittings. They are a small part that connects or ""Couples"" one part to another. They can connect pipe to pipe, pipe to fitting or even fitting to fitting. Some of them even reduce so you can connect a small pipe to a large pipe or vice versa. PVC Coupler, Coupler, SCH 40 PVC Coupler, Bryant Plastics 122-008-6-S, wilson industries, wilson