PEX clamp (cinch) rings

Entry in Joining methods · Updated October 29, 2026 · Written by the Know Your Pipes editors from the sources listed under References

A PEX clamp ring, or cinch ring, is a stainless steel band with a raised tab that a ratcheting tool squeezes shut to hold PEX tubing on an insert fitting.^[1] In the PEX clamp vs crimp choice, it replaces the copper crimp ring on the same fittings.^[1] The ratcheting tool only releases once the clamp has been fully closed.^[2]

1 Standard and compatible fittings

ASTM F2098 covers stainless steel clamps used with insert fittings made to ASTM F1807 (metal) or F2159 (plastic), on PEX tubing and on PE-RT tubing.^[1] The standard describes the clamps as an alternative to copper crimp rings and rates the joints for 100 psi hot- and cold-water service up to 180°F.^[1] Because they share fittings, the method is closely related to PEX crimp rings.

One maker sells its clamps in 3/8 in to 1 in sizes for brass and plastic insert fittings on PEX pipe.^[4] Its clamps are annealed 304 stainless steel.^[5] Its instructions forbid using the clamps on PEX fittings made of copper, because leaks may result, and limit them to brass or polysulfone (plastic) insert fittings made to ASTM standards.^[3]

2 How the connection is made

The tube is cut square and deburred, the clamp is slid on, and the fitting is pushed into the tube until the tube stops at the fitting's shoulder.^[3] In that maker's instructions the clamp then sits 1/8 to 1/4 in from the tube end, directly over two barbs, before the tool jaws close on the tab at a right angle to the pipe.^[3]

The joint is checked by looking at the closed tab rather than with a gauge.^[3] Pliers or other non-ratcheting tools are not acceptable and can leave an improper fit that leaks.^[3] The maker's specification also calls for the tool to have the proper sized jaw and to be field-calibrated on a regular basis.^[4]

3 Limits and cautions

When connections are made below 30°F, the maker warns that the PEX needs time to seal against the barb and says to close the clamp slowly.^[4] It also lists products that can damage its polysulfone fittings, including pipe dope, leak-check compounds, cleaners, solder flux, plastic pipe primers and cements, and spray foam insulation.^[3]

Clamp rings make a permanent joint; a bad one is cut out and remade. Fittings with wider bores that need no ring tool at all are covered under PEX expansion fittings, and tool-free joints under push-fit fittings. Local code and the tubing maker's listing decide which of these may be concealed in walls.