This product information service server device retains product size information that associates each of a plurality of manufacturer's sizes for each of a plurality of products with measured product dimensions for that size. When a product has been selected for a body part of a user, the product information service server device finds a set of measured product dimensions (if any) that is provided for the product, and that matches dimensions of the body part, and identifies the manufacturer's size corresponding to the set of measured product dimensions, on the basis of the product size information.
