These Heavy Duty Tappets have been drilled for extra camshaft oiling for Triumph TR250, Triumph TR6, Triumph GT6, Triumph Spitfire 1965 (From FC61023E to 1980, 1500 MG Midget. They are tuftrided for long life and heavy duty use. Every batch of tappets are tested when they arrive from the UK. Each tappet will have a minimum hardness of Rockwell 58. 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. The term for these tappets in the US is Lifters, other use the term buckets, all of these terms are interchangeable and refer to the same product.