For all 912 engines and also suitable for 356 engines (3-piece type) -- this is the inner half of the generator pulley assembly with notches on the edge. See your owner's manual for loosening the nut with a screwdriver wedged in one of the notches. Finish is gold iridite to match plating commonly found on 912 engines.

A silver plated version is available, see: NLA 09 315