I found that while the pens are great for marking diagonals on binding fabric and triangles, the are definitely NOT great for marking stitching lines for quilting. I was marking a pretty complicated pattern for a whole cloth quilt and was interrupted for a while. Then, discovering that the pattern needed a small change, I pressed the area and found that the pen had stained my fabric and ruined the whole thing (thankfully it was a small quilt and not bed sized)! I am back to using the water soluble blue markers.