I chatted with a well-known 221 man from Florida while at Paducah this spring. He says there are NO PLASTIC bobbins made for the FW. That is true. I have searched most of the Ebay sites for some. I was able to obtain 50 metal bobbins from Manny Saler in New Jersey. They have been wound on a mechanical bobbin winder like the one from Wal-Mart and have been working flawlessly. No, they are not a 66, or 15. They are only used on the 221 FW and the 301 Singer. Buy the best you can afford. Never skimp on bobbins. Sew-Classic.com is a good source for good quality at a reasonable price. They ship fast and Jennie knows her stuff in case you have more questions. Good luck.