We should have a party for bear-is-gray, this is a quilter who knows! Agree that you should use the bobbin cited in your manual. I always thought that a metal bobbin would be the thing to use so I ordered the correct bobbin in metal instead of plastic to give it a try. Big mistake, there were little (tiny) pieces of metal that got caught on the thread and talk about a "bird's nest?" It was more like a rat's nest. Luckily I didn't buy a bunch. There are two sites online that have charts, one of them is sewingpartsonline. Sorry I don't have the exact link, but if you type that into Google it brings up the site link. I have little colored boxes for bobbins to each machine and a cookie tin for the bobbins for the main machine, all are labeled. Wound bobbins are in those round rubber bobbin holders from Nancy's Notions and other wound bobbins are on the bobbin trees, also from Nancy's notions. Organization is almost a necessity in quilting. That said with such conviction and I find that after each project is completed I have to re-organize because I've pulled out so many tools, etc.