I have always had Bernina machines and did not think I could use pre-wound bobbins, but was told to carefully remove the cardboard sides and they work just fine - have never had one unwind.

I got a package of pre-wound cardboard bobbins. the thread wasn't in the best shape so I use them for hexies or any other epp projects. Again the thread wasn't the best.

Yes, they are prewounds. Aside from the paper, though, you have to make sure they're the right size for your machine. The wide flat ones say Class F, and I don't know any domestic machines that use that class of bobbin.

The smaller, taller ones with white thread look like they might be class 15, which is used by many Janomes, Kenmores, Brothers, and of course the Singer model 15 machines. Measure and compare the size to a bobbin that you know works before trying it.

I think the F size fits a Featherweight.

My Aunt worked in a men's clothing store that closed. She gave me many similar bobbins. I use them on the top of my fabric and rewind other to my sewing machine's bobbins. They work okay.

Are you sure that is cotton thread? I have a few spools of silk thread that is sold on spools just like that from when I could see to do beadwork.

I looked again at the bobbins my Aunt gave me. All of them have the letter L either printed or imbedded on one side of the cardboard. Only have 1 with white thread and it has the number 40 printed on the opposite side of the cardboard. The dark gray thread has THREADS and USA imbedded on the opposite side of the cardboard. The brown thread has ATCO printed on the same side as the L and on the reverse side is SPUN 50 DEE and what I think is a trademark -- a star with a circle around it. There is more red printing around the trademark and I can't determine what it represents. I know in my lifetime (78 years) I've seen thread with a star as part of its trademark.

those are prewound for professional machines

Lynnie, thank you for confirming what I thought. My Aunt worked as a sales person in a small men's clothing store before the owner retired. He gave her many cardboard bobbins filled with thread colors used in men's clothes. I rewind the thread to my bobbins. Have been happy with the thread.