Expansion fittings provide an exceptionally secure, full-flow connection method specifically designed for PEX-A tubing. This system utilizes the unique thermal memory of PEX-A pipe. An expansion tool is used to temporarily stretch the pipe and an outer expansion sleeve (or ring). The fitting, which has a larger inner diameter than crimp-style fittings, is then inserted. As the PEX-A pipe naturally contracts to its original form, it creates immense and continuous radial pressure around the fitting, resulting in a permanent, watertight seal that is stronger than the pipe itself. This technique creates an unobstructed flow path, maximizing water pressure and system efficiency.