Aftermarket (A/M) is used to describe parts that are produced by a manufacturer other than the one who originally made your car. Some aftermarket parts carry certification that helps ensure the basic quality of the part. Aftermarket parts are usually less expensive than new OEM, but for some applications may be a better choice than used OEM parts. While it is not the practice of Dorn’s, some repairers and insurers list these parts as “Quality Replacement Parts.”