I have several cones of Overlock thread and Surelock thread for my 2 regular sewing machines. All the cones of thread that I have have a sticker on the inside of them saying that they are 100% polyester thread. These cones come with 3000 yards of thread and are much cheaper than a regular spool of thread with much less quantity. I have a Dritz gadget that I can place these cones on my regular sewing machine and they stand up on the spindle just fine. I"ve spun bobbin thread from them and they work just fine, just don't forget the plastic cone thread adapter piece. If you use cotton flannel or cotton fabric for a quilt or anything else large, what is the question about using polyester thread on cotton material? I've never had a problem with either of my 2 vintage Kenmore machines. from, Debbie, Phoenix, AZ