Malossi Fly Clutch Kit for 50cc 4-Stroke 139QMB, Aprilia, Derbi, Vespas ScootersSPECIFICATIONS: Outer Diameter (clutch bell): 115mmInner Diameter (clutch bell): 107mmOuter Diameter (shoes): 104mmClutch Bell Inner Diameter (splines peak to peak): 11mmClutch Bell Inner Diameter (splines valley to valley): 11.85mmNumber of Splines (clutch bell): 22Fly Clutch is a reinforced centrifugal clutch designed to easily withstand extreme operation, for example, constant stop and go on steep roads, city traffic, long series of traffic lights, especially with a passenger, and during hot weather when it becomes difficult to control scooter temperature levels.Fly profits greatly from Malossi’s experience, results acquired from research and thousands of tests performed in the field of scooter racing.**