The Weights or Points for Item Options feature allows you to add weight or points to the total weight/point value for specific items. This is based on the available options for the particular item.
You sell an item that comes in two sizes. The size is selected using options in a drop down menu. The small is the default size, and weighs five pounds The large weighs seven pounds. This feature automatically adds two pounds to the default size weight of five pounds(the difference between the small and large).