I used them once.My TTIs leaked like no gasket was there.Pulled them off and went Mr Gasket Ultras.This set has been on since I put the new heads on like 5 years ago at least.We run them on all headers and even pulled them off and reused them.Only place I use coppers is on the collectors.To me the copper and alumiun are junk.20 bucks for Mr Gaskets and years of leak free headers.Rocky