decided to buy new bobbins for my singer 6268. I spent all day trying to fix the bobbin case It sewed great but when it came time to remove the fabric the bobbin thread would not pull out, it simply broke off every time. After remembering I had just purchased bobbins at Joann I decided to wind up an old bobbin. Couldn't believe the new bobbins were defective! They have a small metal center the sits in the center of the bobbin. It is extremely hard to detect this flaw. I'm just writing this to aware someone having trouble with their bobbin thread to check out the bobbins if newly purchased. These bobbins are singer Centaur ll bobbins. They are 2 to a pack. It might save a service call. Thanks for all your posts