Product review (5 stars): All that was needed for an easy fix!
Exactly what was needed to get the Whirlpool agitator working again.  Made sure to order the part offered by Amazon, arrived and showed it was a Factory Certified Part from Whirlpool Corporation.  Lots of videos online show how to get inside the agitator from the top and swap these parts in.  Over time, they wore down and after a 5 minute swap, looks great and when turned counter clockwise, you can see the agitator locks in and spins.  Easy to see the difference when comparing to the old ones that have worn down.