Featherweight bobbins are much thinner than a class 15 and are unique to Featherweights and 301's. There are no plastic bobbins and the metal bobbins have holes all around the outside of the bobbin. I find that sewing machine sales places here in Southern Ontario stock them. I've bought them at Triangle Sewing Centre in Guelph and the Markdale Sewing Machine store. Prices have ranged from .40 to $1.00 per bobbin.