Here's another vote for Connecting Threads. Not only is it great quality for a lower price than poly/cotton from your big box stores but my fussy machine likes it. Also, I love the fact that it has a simple straight spool. The ones they try to make fancy with wide bases, narrow tops etc my fussy machine won't accept half the time because I can't reverse the way the spool rests. My old Singer plods through anything but not the other machine.