When I started quilting I had a large selection of partial spools from garment sewing. It was a mix of 100% cotton, 100% poly and also blends. I asked a quilter if I could use these for piecing and they said no problem. I will say that when I ran out it was recommended that I use Aurifil 50wt and I wouldn’t use anything else now. I am able to purchase from my LQS and it is fine but strong....there may be something better but for me it’s one of those if it ain’t broke don’t fix it situations!