Certified Auto Parts Association. I just bought a tailgate from Rockauto and I did get the CAPA certified just for a piece of mind even if there is no difference. What it comes down to is most issurence companies will only uses aftermarket body parts that are CAPA certified. I remember back in the day if it wasn't an OEM part it would fit like shit but they have gotten a lot better over the years. I can't really tell the difference between the 2 tailgates as right now but I will give you an update once I get it back from being painted.