I have some that are cotton and some that are poly-cotton...the cotton ones hold less thread......I only use them on my longarm.......they are wound tighter and I can go "farther" with them....never have used them on my dm, I have the habit of winding 2/3 bobbins before I begin my piecing day...using a neutral thread like beige, gray or white and when I do embroidery (rarely) I will wind a bobbin with lingerie thread...thin, poly..works for me........again, we work with what works for us

That's all I use. I keep stock in gray, off white, tan for most of my piecing. I rarely wind a bobbin. I buy black and white in the 144 quantity. I found the cardboard sides were undesirable for me and use only the plastic.

I also use mostly poly or rayon thread on top, I have LOTS of that kind of thread for my embroidery machine and have not had a problem.

I may be wrong but my machine uses "L" and class 15, one is just wider than the other. I use the metal pin insert with the L bobbins and the class 15 is the same width as the bobbins that came with my machine. I also use a penny under the bobbin when I misplace my metal pin.

I have to respectfully disagree, and I also teach quilt classes, as well as work on the vintage machines. While I do not use pre-wounds, it is because I do not have a machine that will take them. I do use the thinner bobbin thread on nearly all of my work now, from piecing to machine quilting. Yes, conventional wisdom is to use the same thread on top and bobbin, and I do this when balancing tension on machines that are in for service. However, so far I have had no difficulty when switching to the bobbin thread. Yes, sometimes a tension adjustment needs to be made, although that has not been anything major nor difficult.

And embroidery thread is usually much heavier than bobbin thread.

Sorryto have to disagree - but Bottom Line is also for embroidery. This is straight from Bob of Superior. I use it for all my embroidery. It's also GREAT for Stitch in the Ditch, because it's so fine that it disappears. I bought all of the BL assortments at the Tucson Quilt Show a couple of years ago, and last year I bought big spools of BL in the colors I use the most. Love BL thread!

I love the pre-wound bobbins they have more thread on them than you can put on your regular bobbin so quick fast and dependable! And yes the bottom line is wonderful for applique you can also get the pre-wound bobbins in different thread weights as well as fiber content.

The Bottom Line bobbins in plastic are meant for appliquers - the thought being that cardboard would fray over time; whereas, sitting in the bobbin case it does not.

I also use prewounds. I asked my sewing machine repairman if they could be used in my machine (Babylock Quest+), and he gave me one to try. It was wonderful!!! They last forever, and help achieve a very accurate 1/4 inch seam because there is less bulk. I purchased 100 bobbins for $32!!! I've been using them for piecing and quilting, including FMQ, with no problems! By the way, mine have NO sides, cardboard or plastic.

I tried the cardboard-sided bobbins and will not use them again. The plastic prewound cost more, if you can find them, but they are better. Really saves time. May husband bought me a bobbin winder, which really saves time, too. You don't
have to rethread your machine.

QUOTE=LoisM;5675144]I'm doing a bit of on-line browsing today and came across pre-wound bobbins in a variety of attractive color tones. They seem awfully convenient.

https://www.superiorthreads.com/shop...-set-2-pastel/
https://www.superiorthreads.com/shop...-set-1neutral/

I have a Janome 4800QE and have yet to see pre-wound plastic bobbins with 100% cotton thread. I'm kind of reluctant to use cardboard-sided bobbins and, besides, I really don't want to use poly thread in the bobbin if I'm using cotton thread on top. What has your experience been with pre-wound bobbins? Thanks everyone!! I'll be waiting to hear from you. :)[/QUOTE]

I use a prewound bobbin bought at a quilting store with 100% cotton thread. I love them. Wish I knew what kind they were but they are class 15 bobbins and cost around 7.00 for 8 of them. But it been a while since I bought them.