Some of you may have read my previous post about me buying silicone o-rings for the ATpro. I had bought 7/16 OD o-rings the first time. They fit real tight on the connectors and let them slip right in with no issues. But then I thought that Garrett may have meant 7/16 ID o-rings? So I bought some of these. I can tell you with 100% certainty that this is the o-ring size that is correct. But even being silicone with fresh grease on them they still want to slip out of the groove and get cut or sheared. I'm glad I bought a bag of 100.