I LOVE the pre-wound bobbins for quilting - I use a size L in my Singer 15's, Lady Kenmore 89, Kenmore 1802 and Kenmore 1803.
The shiny thread looks beautiful on the backs of the quilts I've used it on and a bobbin lasts a long time (a little over half an hour of steady FMQ)
I buy a gross of them for about $30 and I think I figured that with shipping, they were costing about 25¢ each. I use 6-12 bobbins per quilt. (I normally use more bobbins than that, so I think the bobbins hold quite a bit more thread than those I wind on the machine.
I'd like to find something similar with matte thread - maybe even in colors like natural, light grey and black. A very fine thread like this shiny stuff, only looks like cotton?
Anyone got a source for pre-wounds like that?