I bought this metal grinder set to replace a plastic grinder set I had.   I also have a professional grinder for larger commercial mixer.
this Kitchenaid Metal Grinder set w/ the discs is of the same quality as the commercial, but sized for the home chef and regular Kitchenaid mixer.    it comes complete w/all the attachments to produce professional quality results in sausages, pates, and ground meats for different dishes.   
if you wish to do your own grinding, this the best non-commercial attachment I have seen in all the brands out there. [This review was collected as part of a promotion.]