I didn't even know there was a "J" bobbin! I'll post if I find any in my internet searches. Looks like bobbins are going the same way cell phone charges are going - they each have their own unique size. I suppose now it won't be long before each sewing machine company has their own bobbin size so we'll have to buy only their bobbins. Which means they'll be more expensive. Ugh. That's gonna make it hard to find bobbins to match colored thread, for sure!