Joe, I bought some Singer 66 bobbins at Walmart, and I think they didn't fit just right in my bobbin holder and would stick in there and not move around in it. I can't remember just what they did, but they were just the wrong size for the Singer 99 machine. Maybe they will work in the newer 99's but the one I tried them in was from 1928. Others have found also that they don't work in the vintage machines. I think the ones I get from sew-classic are better made ones, and that might be just why the others didn't work. I took the ones I got from Walmart back, and don't plan to get more from there. Since I had the trouble with the Singer ones I got at Walmart, I haven't gotten any of the Singer bobbins for my FW either, but have gotten them from sew-classic instead. I hope this answers your question. If not, maybe others will tell you of their experiences with new Singer 66 bobbins.