Granted, my equipment maintenance experience involves rebuilding two Conshelf firsts and three seconds. That said, replacing the o-ring inside the QD for an inflator has been the must frustrating excercise, by far. I guess because it is relatively deep? It was also a hardened oring so I had to use the pick to break a small chunk out before the rest would come out. If I have to do that again it will be too soon.