KitchenAid's website, as well as Sears, Appliance 411.com and PartsSelect.com all have parts diagrams available to assist in correct part selection. Generally, the model number of the appliance is needed to access the correct parts diagram.
In most cases, the model number will be on a sticker or metal plate in an easy to locate place. If the model number sticker or plate is worn off you can use the manual to identify the correct model. The KitchenAid website has manuals, warranty guides and installation instructions in addition to parts and electrical diagrams. The company also offers a toll-free number for assistance, live chat online and email requests to assist in parts ordering.