Different sizes is just the beginning. I got mine from Advance Auto and we went through every size available. The really weird thing was that the cups for the shaft pressed in perfectly but, the cups for the yoke were too small. At first I thought that it was a screw up so I took it back and they pulled another one from stock but I had the same situation. We then tried all the different available u-joints and I wound up getting my money back while they looked for another vendor. I then went to National Auto stores and ordered a u-joint from them. It was from a different manufacturer. This one was just the opposite, the cups for the shaft were too big but, they were just right for the yoke. So, I just swapped the cups and went on my way. I hope that this was just a fluke, cause I don't want to go through that again.