I cannot use Filtec Essence monofilament because Filtec warns not to iron over it (it is nylon) and you have to watch the heat when drying in the dryer. Monopoly is polyester, can be ironed, and since I use it mostly for art quilts that I layer-stitch-layer-stitch it works well. If you’re using a spool, make sure to use the vertical spool holder, not the horizontal. When I used the horizontal spool holder the thread stretched much more. The vertical spool holder allows the thread to come off the spool naturally.