The Polini Evolution gear cover, unlike the original gear cover, is made with a needle bearing for both the middle and the secondary axle (rear wheel axle). This helps to provide significantly less resistance in the gearbox and thereby get a higher performance. The gear cover comes with a special viton stuffing box, with a Teflon insert. This helps to reduce the friction in the gearbox and on the primary gear shaft. The gearbox cover also comes with an O-ring gasket which provides a completely tight gearbox housing.