WTC I just think they tried to over engineer them. Those little disks on the bottom of the holder is a good idea, but it may only work on one boat for all I know. They will work for a 393 Ranger but I couldn't for the life of me get them right for a 522. Threw them away and got it where I could tighten them down, and haven't had one minutes problem. Bert Bennett is the one who showed me about the bolts. He is on their pro staff so I hope he has told them about it.