I have a very good supply of several different threads. I so like to long arm with SoFine and OMNI. Both are poly threads by Superior. I used cotton threads such as Aurifil, Mettler, King Tut. They all worked fine in my machines. I think one thing you can do is try and break each thread. I have tested some threads where you can easily pull them apart seeing the thread unravel. That I would give a strong NO. Good to look at how much thread is on the spool or cone and the price per meter or yard. I think a meter is about 1 yard, 4 inches. A large spool of Gutterman 50 weight cotton is 800 m (876 yd), A large spool of coats and clark general purpose thread is 274 m (300yds), and a large spool of superior's 60 wt the Bottom Line is 1,420 yds. A cone of SoFine 50 wt is 3,280 yds. Small spool of Aurifil cotton 50 is 200meters, the large spool is 1300 meters. A large spool of Aurifil cost $14 The last time I was in a shop. The large spool of Aurifil looks to me like it would hold a little more then Gutterman but actually holds 500m more. I was thinking of using SoFine to piece with once I used of more my Aurifil. One is cotton, one is poly. Question is poly a plastic? I have been reading about all the nano particles of plastics now in all of us.