Could someone please tell me what kind of bobbin #541090 is? I know it's transparent. Thank you!

Sorry, it's singer brand bobbin

https://www.manualsdir.com/manuals/7...44.html?page=5

I think it is just a replacement for the metal bobbins.

It appears that it is a class 15 bobbin. I did a google search https://www.google.com/search?q=sing...t=gws-wiz-serp
for singer bobbin "541090" and found several machines that list that number for bobbins such as 5122, 3015 5102, and 4012/4022. I found these pages for bobbins that fit those machines at https://www.sewingpartsonline.com/bo...0pk-81348.aspx and https://www.sewingpartsonline.com/bo...c-10-pack.aspx

Janey - Neat people never make the exciting discoveries I do.
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