A: Easily the most recognized difference is “fit”, the way the parts line up with the rest of the vehicle. Imitation parts makers must use a “reverse manufacturing” process, that is they take a new OEM part, make a mold, then use the mold to make a press to actually stamp out the parts. This process is inaccurate, and allows much room for error and variance. Typically, when an A/M part is installed on a vehicle, the gaps and body lines do not line up properly and the part needs to be shimmed, mounting holes need to be slotted, or the part needs to be otherwise “reworked”. Another concern, not as immediately apparent, is the corrosion resistance of the “Imitation” parts. Most OEM parts are zinc coated or galvanized to help resist rust and corrosion whereas most A/M parts are not. This may not present a problem for several years.