All cars have a required performance kit (wheels, tires and suspension) that is required to run in its class. They also each have optional modifications, intended to make the cars more durable for motorsports and easier to maintain. For those who want to race or HillClimb their Club Spec car, or just want more safety for Track Days and Time Trials, there are also safety allowances for each car. Each is a little different, and all are specific (hence, spec) so make sure to check the CSC, CSX, and CSM rule pages for all current requirements.