This simple tool eases installation of your rocker shaft with new o-ring into the rocker box on your Triumph or BSA motorcycle. This tool can be used on basically all Triumphs, 350cc, 500cc, 650cc and 750cc, as well as BSA A65 and Rocket 3. The taper on the inside of this tool eases the transition of the o-ring into the groove in the rocker box, and without it, the o-ring typically gets cut or shaved when pushing the rocker shaft home. The taper allows the o-ring to be installed, undamaged, resulting in a leak-free install! CAD plated, made in the USA. This is a replacement for Triumph factory tool OEM # 60-2221, Z111