PEX fittings are adapters, elbows, couplings, etc. that connect PEX tubing and are generally made of brass, copper or polyalloys. Ridges on the "insert" side of the fitting are what distinguish it as a PEX fitting. Those ridges, the PEX tube and crimp rings (typically copper) all combine to provide a high-pressure seal. Products vary by fitting shape, connection type, maximum pressure, pipe size and tube size, among other attributes. See our press tools and accessories for ideas on the best way to put the right crimp on your tubing connections. And, just for reference, “PEX” stands for “crosslinked polyethylene”.