Tappet for MGA and MGB 1963 to 1971.  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. Cross Reference 460-660