An aftermarket car part is any part of a vehicle that is not sourced from the car's manufacturer. Aftermarket parts are reverse engineered from the original parts, sometimes improved upon if weaknesses are discovered.
Aftermarket car parts generally have greater availability than original parts due to the large amount of aftermarket part companies. Some companies specialize in specific parts, while others create almost every part of the car. Aftermarket parts are available in more locations than original parts, with many being available at local gas stations and auto part stores. Aftermarket parts are typically not used by car dealerships for repairs, choosing to use original manufacturer parts instead.