I use Superior threads So Fine in the top, and Bottom Line in the bobbin...although not ALL the time. I play with Connecting Threads (Gammill doesn't like it much...), have tried Glide, and I personally really like King Tut. I've tried the pre-filled and also the magnetic core bobbins; both work equally well in my machine. Don't care for Aurifil, altho lots of you all love it...guess I would too, if my machine liked it. Hope that helped...