ASTM F2159 specification uses a copper crimp ring to compress around a fitting.
F2159 Pex Crimp Fitting CouplingF2159 Pex Crimp Fitting ElbowF2159 Pex Crimp Fitting Female AdpteF2159 Pex Crimp Fitting Male AdapterF2159 Pex Crimp Fitting PlugF2159 Pex Crimp Fitting Tee