I prefer very thin thread in my bobbin at least a 70wt. WonderFil is 100wt and is great. I can use a 50wt 3 ply thread, like Connecting Threads Cotton when I use a thin thread in the bobbin. There are a lot of thin thread brands to choose. There are so many good brands of thread being manufactured now. Glide by FilTec is a new favorite of mine. For applique I use YLI silk thread because I have a lot of it and my stitches don't show with the silk thread. I use the silk thread for handsewing bindings on my quilts. Superior now has silk thread in many colors. I love silk thread.