This feature details the type of in-dash car stereo receiver that the item you are viewing is compatible with or made for. A Factory or OEM stereo is what is included when the vehicle is manufactured (eg. the original Ford car radio is the OEM or Factory stereo). An Aftermarket car stereo refers to a car stereo made to work in many vehicles. Aftermarket stereos are made by companies such as Sony, JVC, Dual, Jensen, Pioneer and others. Universal compatibility refers to an item that works with any kind of car stereo receiver.