I thing Dritz has two different lines of bobbins, decent and junk.
The bobbins in the plastic 10 packs all seem to be the junk version, while the bobbins on the card are the better ones.

Joe

Thanks for the tip about the Walmart 66 bobbins. I use 66 in one of my Singers and 15 in another. I buy them at Joanns and haven't had any trouble with them.

I had the same happen to me with the bobbins. we to sew classic and new ones that work.

I don't use any new bobbins in my featherweights anymore as I'd bought a package @ Wal-mart and a bobbin got stuck in my bobbin case. I thought I'd never get it out, the bobbin wasn't quite round. What a nightmare.