This drift allows you to remove and install the tappet blocks on your 500, 650 or 750 c.c. pre-unit or unit construction Triumph motorcycle to replace the o-ring, or when removing the cylinder for paint or machining work. This is the proper way to drift the block out without damaging it. This tool can also be uséd on Triumph Trident and the BSA Rocket 3. Triumph factory service tool # 61-6008.