upper section of agitator not turning

I "googled" "Washing machine agitator not working". It guided me to a site with a "you Tube" video of a appliance repair man fixing the problem on similar machine showing the worn dogs etc and how to replace them correctly. The site also provided a link to PART SELECT web site with all the info needed to order the correct part for my washer. Very simple!
I would like to add the service/delivery from Part Select was excellent!! I ordered the part online Saturday eve it arrived the following Tuesday.