Like carolaug, I use Gutterman 100% cotton thread for sewing seams in quilts and for my garment sewing, which is mostly linen. A few times I have accidentally picked up Gutterman's quilting thread, which is thicker. It makes a difference in finished seams, I think. One of my favorite sewing gurus, Louise Cutting, recommends in all of her garment patterns to use 100% cotton thread for sewing the most professional seams-- after pressing correctly of course.