Directly from One of the Biggest Pex Systems Manufacturers 5 Pack 1/2" Pex-A Expansion x 1/2" PB Transition Brass Pex Coupling Adapter With Rings, Lead Free Compatible with all Types of Brands of Pex A Pipe/Tubing and PB Pipe Pex Thread Compatible with Expansion Fitting System, NOT Compatible with Stainless Steel Clamp & Copper Crimp Ring Systems Certified to ANSI/NSF-61 and ASSE 1061 Product Standard. Meet the Standard F1960; Resistant to Corrosion Due to DZR Brass Larger Internal Diameter Expansion PEX fittings Results in a 25% Greater Flow Rate Within the System