Product review (5 stars): Worked to fix my washer's agitator
I noticed that my washer's upper agitator was not working properly when turning against a full load of clothes.  Not an expert in appliances but some online research indicated that small plastic parts called "agitator dogs" within the agitator are common wear items that need replacing periodically.  I opened up the agitator and confirmed that they were bad, but couldn't decide whether the rest of the components in the agitator cam were in good shape or whether the slight wear/debris I observed might have been contributing to the failure.  I opted for the more conservative (though slightly more expensive) option of replacing the whole cam assembly using this part.  Suffice it to say, it worked and the agitator started working fine -- though I now conclude most likely replacing the "dogs" would have been sufficient in my case, I don't regret being cautious.

One thing to note, this cam design has an unusual 1/2" square socket used instead of a normal bolt.  I'm sure there's a proper tool but I didn't have it... so I used a 1/2" square metal rod obtained from a home improvement warehouse to fit the socket and it worked fine.  It cost just over $3.