Polini 15/42 Gear Set for Minarelli 2-Stroke Scooters. Higher Gear Ratio for increased top speed and lower RPM while running at top speed. It is recommended this gear set be used after installing a big bore cylinder kit. A stock engine will not have enough power to make use of a taller gear set. Fits the following models with Minarelli engines:Aprilia: SR50 and Scarabeo 50Benelli: Pepe 50Malaguti: Ciak 50, F12 Phantom and F15 FirefoxYamaha: Zuma, Zuma II, Jog, C3 and Vino 50cc 2-StrokeMade in Italy! Please see our Warranty & Returns Policy.