PETMA112 Poly Insert Male Adapter, 1-1/2 Inch. An adapter is designed in order to connect two sections of piping together. It features a barbed connection on one end, which allows the poly pipe to be slid onto the fitting. The other connection has a male threaded connection, making this fitting a barbed by male thread design. The coupling design of this fitting lets you connect two sections of 1-1/2 inch poly pipe. Poly fittings are used in multiple water applications but should never be used in gas, steam or compressed air applications. The fittings are specifically designed to work with polyethylene tubing (aka Poly Pipe, Poly Tube). In order to create a secure and tight connection, hose clamps should be used. The barbed connections of the poly fittings work well to hold tight to the pipe, but water pressure can push the tube off the fitting, making the hose clamps a great choice for installation.