Product review (5 stars): This part fits the Costco model Kitchenaid 6 qt bowl-lift stand mixer, ie KSM6573
This part fits the Costco model Kitchenaid 6 qt bowl-lift stand mixer, ie KSM6573 / Professional 6000 model.  It works great kneading bread dough for me.  There are few reports in the reviews of the mixer that the white coating on this hook started falling off.  I have been using mine regularly a few times a week for 3 months and no problem.  I handle it gently, wash it carefully by hand, polish it with a cotton dish cloth and never touch it with abrasive scrubbers, etc.  They are fairly inexpensive so you can buy a spare or two in case the coating ever starts to shred.