PEX clamp tool is a universal tool which works with all five major sizes of PEX: 3/8", 1/2", 5/8", 3/4" and 1". It’s used in combination with PEX cinch clamps of corresponding sizes to connect PEX pipe to crimp style brass or poly PEX fittings. These tools are factory calibrated and feature a mistake-proof ratcheting mechanism, which releases the tools’ jaws only when connection is complete.