I purchase Madeira 100% polyester pre-wound. ;)

The NEBS prewound works best for me. They are plastic sides and don't cause the lint that I get from the paper sided bobbins. Since they have sides period I am able to use up more of the bobbin thread without wobble when they get low on thread.
Marcelle Lewis (lewismm@bellsouth.net)
http://embroidery.gotop100.com/
http://embroideryavenue.com/

I use metroemb.com prewounds with the plastic sides and have had no trouble with them.

Hmm...seems like plastic sided pre-wounds are pretty popular here. Have you tried the Coats, or Coleman brands? I have also heard of a bobbin with a magnet inside the middle that is supposed to keep your bobbin balanced and spinning smoothly. Anyone ever try these?

I use NEBS prewound or finishing touch for bobbins I need to wind.

I don't know the name of my pre-wound, but I buy them locally from the place I got my Brother. The repack them and it just has "poly" on the side, but it is very very thing thread. :) I love them.