Sioux Chief 558-M series PipeEye metal stud insulators can be used where necessary to insulate and isolate CTS copper, PEX or CPVC supply lines from contact with metal studs or galvanized brackets in residential or commercial applications. Insulators are designed to fit 1-11/32" diameter hole. 558-M23 series shall accept both 1/2" and 3/4" CTS tube. All insulators are IAPMO certified.