Beth, I have a Brother PC8500, and at a sewing conference recently (sponsored by Brother) they said that JP Coats prewounds were the best for their machines. They have cardboard sides. I guess the cardboard creates less friction on the bobbin thread in the high-speed emb. machines.

I bought a box but haven't had time to try them yet.

I have the Brother 150 and the ULT2003D. I've used the carboard sided bobbins with both machines. No problems. I've even been using them for my quilting. I purchased the bobbins at www.goodfortunethreads.com. I think there was 144 bobbins in the box and the cost was $36.00.

I have a Bernina Artista 180 and use the cardboard style for all my Embroidery projects. I found a great deal on a gross, the price was only 22.84 and 7.00 shipping.

I have never tried the sideless or the plastic ones since I only got this machine about a month ago from my FIL it was my MIL's who passed away in Dec. She had already given me her old Bernina Deco 500 machine but this is so far above that one that I am having a ball embroidering everything in site!

Here is a link that might be useful: Embsupplies

Beth, I've now used a few of those cardboard sided prewounds in my PC8500, and they worked just fine!

plus the prewound bobbins have much more thread on them than when you do it yourself. I also buy them by the gross for my brother machines.