These are Heavy Duty Tappets (Lifter) or a TR3-TR4A. They are lightened and have an extra oil drilled in the side for extra lubrication. Every batch of tappets are tested when they arrive from the UK. Each tappet will have a minimum hardness of Rockwell 54. The industry standard is 50 for tappets. We have never had a bad batch of tappets like other companies and never will because of our dedication to dealing with only quality suppliers.