This was our first time replacing this part of our office chair. We were not the ones who assembled the chairs originally and we weren't sure how to do these. They didn't have any instructions for them and at first we thought we did it wrong. They just click together...more or less. After we figured it out it was simple, but we were lost without the idiot proof instructions of put part A to part B nonsense. For our chairs they fit well and went on easily. Overall happy with the purchase.