There are certain criteria which one must be aware of before going out to buy aftermarket car parts. Firstly you need to be aware that installing an aftermarket car part may null your vehicles warranty, if there is any. Therefore, be sure to check your warranty documents before proceeding to install a car part. Secondly ensure you know your car make, model and year as these are the common criteria used to check whether a part is compatible with your car. Finally be sure to check your local laws as installing a certain type of part may be deemed illegal in your area of residence.