Kyosho Mini-Z Ball Bearing Set (7)This is an optional Kyosho Ball Bearing Set, and is intended for use with the Kyosho Mini Z MR 02 and MR 03 chassis. These replace the standard kit bearings with high quality precision bearings that will help to reduce friction and increase run time. The package includes seven bearings, four for the front wheels, two that are installed inside the motor mount, and one goes on the rear wheel closest to the gears and differential.