In my case, I was replacing Moog ball joints that I had installed a few years ago, the last time I changed engines and K members. The new upper ball joints from Rockauto looked different. So I went to my local O'Reilly's and ordered another pair of Moogs. They looked like the ones I was removing down to the last detail. The ones from Rockauto had noticeable differences when laid side by side to the other ones. They were similar, but different. I sent pics of them to Rockauto side by side making a note to them that I thought that they were not really Moog pieces. All I got in response was a return authorization. So, they went back to RA and I installed the ones from O'Reilly's.

Now, I use the Proforged lower and tall upper ball joints. http://www.proforged.com/