I found one importer in the US that carries these expensive Fuji shoulder locknuts. These zinc-plated nuts are identical to the OEM nuts securing the Cam Belt Tensioner eccentric. Blades on the head of the nut grip the stud during tensioning. These nuts are used on all 4-Valve Ducatis to hold the eccentric in place. Use more than once at your own risk. They are single-use locknuts.