Bluefin crimp fittings are compatible with PEX tubing. Crimp fittings are barbed for installation inside tubing after which a crimp ring or cinch clamp is used to hold the fitting onto the tubing.
Copper PEX rings are crimped using a Crimp Tool to an acceptable diameter then checked by a diameter Go-No-Go Gauge. Copper PEX rings are designed to go over PEX tubing to lock in barbed PEX crimp fittings onto the tubing. High quality material and manufacturing insure a tight seal over PEX tubing using a pex crimping Tool.