Product review (5 stars): Genuine replacement parts - works great!
For those who are scratching their heads, agitator dogs control the ratcheting spin action of the top part of your agitator.  To check to see if your agitator dogs are working properly, simple grasp the top of the agitator and twist.  It should freely spin in one direction but lock in the other direction (the ratcheting action).  If the top part of your agitator doesn't lock (or slips), your agitator dogs are worn out and need to be replaced.  Other than acting as a drive for the top part of your agitator, it also serves to protect the transmission because the agitator dogs will break if your washer is overloaded to prevent damage to the transmission.

Pros:
- Labeled as genuine factory parts - perfect fit
- Restores full lock of the top part of the agitator to make sure your washer is working properly

Cons:
- Softer plastic material allows the gear nubs to wear out but that is by design

Other:
You may want to pick up two sets (instead of just one).  They're cheap enough to have on hand so that you can restore proper operation of your washer.