1. A method of gauging a size and shape of a mold cavity for injection molding a product, the method comprising the steps of: (a) selecting a durometer for said product; (b) determining an expansion ratio based on said durometer; (c) selecting a product thickness value; (d) identifying a product material which, based on said product thickness value, results in said expansion ratio; and (e) determining the size and shape of said mold cavity, based on a thickness of the product at a plurality of sections of the product and based on an expansion ratio for said selected product material at each section.