After market parts, sometimes referred to as "performance" parts (though this is technically a sub-category) are simply car parts distributed by someone other than the original car manufacturer. People choose after-market parts for a variety of reasons: to increase performance, save money, deal with product availability, or to modify certain functions on their vehicles. Car parts and equipment vary in quality, so if your vehicle has been repaired using after-market parts or you're considering using them; make sure to do your research on the manufacturer to make sure the part you're buying is of the same quality or higher than the OEM (original equipment manufacturer) part.
Sometimes, after-market parts may be used on your vehicle in the event of a repair. Make sure you do a thorough inventory of your car's makeup to determine which, if any, after-market parts have been used. This knowledge can help you in determining how, if at all, if your car insurance will be affected.
Many car insurance policies require owners to purchase separate coverage on their after market parts, especially on performance parts. If you're confused about this, you want to contact your insurance company directly and ask specifically what would be covered in the event of an accident or loss. Would a percentage be covered? Are the parts covered at full replacement value, the actual cost you paid for the part, or actual cash value, which is the cost minus depreciation to date? Is there a dollar limit? In addition, many state laws limit or restrict the use of after-market parts for certain repair jobs, so make sure you know the local regulations as well. Your state's insurance commissioner website can provide details.
In the unfortunate event that your vehicle is involved in an accident, after market parts may impact you in another way. Many auto insurers choose to repair vehicles with after market parts rather than OEM parts. Aftermarket parts are cheaper, usually more readily available, and can keep the cost of repairs down for the insurer, and subsequently the overall insurance premium you pay annually. It's important you know how your policy will deal with repair issues. The type of parts used to repair a vehicle, especially for large scale items, can impact a car's resale value.
If you're planning on selling or trading in your vehicle in the near future, this may be of a greater concern than if you have no plans to get rid of the car. There's also potential for the car parts to impact the safety rating, for better or worse, so don't be afraid to ask detailed questions. It's always in the consumer's best interest to have more information rather than less.