Product review (5 stars): Save yourself a $200 service call !!
Very inexpensive part to complete a very simple repair.  This easily would have been a $200 service call.  If your agitator isn't agitating...this is most likely the culprit.  When the washer is off, if you can freely spin the agitator, then the internals of this part is stripped out and needs replacing.  The agitator slides onto this part with no fasteners, so to remove you simple pull up.  This may take some effort depending on how old your machine is.  Once the agitator has been removed you will see this piece being held on with a single bolt.  Remove the bolt and this part will lift right up.  Reverse the process to install the new one and you are back in business.