I use Monopoly with no problems....I loosen the top tension and usually use Decobob 80 or Invisafil 100 in the bobbin but have also used Aurafil 50 and Gutterman 50 in the bobbin with no problems. The only thing I have to be careful about is cutting my thread when finishing a line of stitching.....I don't use the thread cutter and I make sure that there is no tension on the threads when I have pulled my work out from the needle otherwise when I cut them the monopoly bounces right out of the needle and I have to re-thread it...which is a real test for old eyes!