This design is quite foolish. The top part of the agitator has BUILT IN plastic teeth that engage with plastic dogs. The dogs are designed to make the top part turn in only one direction, pulling the clothes down into the real agitator. I tried replacing just the dogs last year which worked fine for a year. I determined that the teeth on the top part of the agitator were worn out. I replaced the entire top part and the dogs again. Easy job, only one long extension on a 7/16" socket required. All good now. Those teeth lasted almost 15 years so I guess I can't complain too much.