Product review (5 stars): It worked
The parts were what I needed.  When the upper part of the Whirlpool agitator stops working, it is almost always the "dogs".  They serve as ratchets that grip the inside of the agitator.  When they wear down and no longer grip, the agitator fails.  The price was the best I've found and my washer has another few years of life added to it.
Got here fast.