Krysskil / Woodruff wedge / WK 3x13 for e.g. drive shaft 2-speed Sachs and lots of others.
Fits e.g.:
Autoped 31/40cc 2 pcs on 31cc and 1 pc on 40cc
Piaggio Ciao and Vespa 50
Husqvarna Silver Arrow, Gold Arrow flywheel and crankshaft
Yamaha, Suzuki and Ciao