Product review (5 stars): Whirlpool agitator dogs
I purchased the pack of four agitator dogs for my Whirlpool washwer and they worked like a charm.  I chose 3-5day shipping and it took 4 business days to arrive.  Definitely cheaper than a new washer and for less than 5 bucks with shipping you can't beat it. Home Depot and local appliance repair shops were charging at least 15.00 but save your money and do it yourself. See Youtube for assistance with instructions there were several posts.