This tool can be used to make clam shells and orange peel designs.
Classic size: is for APQS & Gammil Machines, these hopping feet our slightly over 1/4" (1/2" diameter).
Petite size: is for all other machines with a true 1/4" hopping foot (1/2' diameter).
Note: APQS and Gammil are beginning to phase in a true 1/4" hopping foot so if you bought your machine after 2016 you should measure your foot to be sure. Also you may buy a true 1/4" foot from your respective manufacturer, in this case you will want the petite size.