Originally Posted by
ArchaicArcane
Mike is right, it's for a class 15 machine. It also would be for a lot of the clones or branded machines. It's -not- for a 15-90 or a 15-91,
Sorry, I was editing that to add something like "301s take the same bobbin/case as a featherweight".
The common 15 bobbin is probably of no use to you. Best keep it in a drawer and look for a 15 clone to put it in
