I used to use a chalk pen for all of my marking (which is a lot) and I just kept having to buy more and more chalk and it was annoying having to sharpen the chalk all of the time.
I finally bit the bullet and bought one of these pens that disapear after 24hrs or so and now I am kicking myself that I didn't buy it sooner!
Not only is it great for marking lines to cut but I have also used it to draw out designes to quilt along! My free hand quilting is much better looking now as I can follow line perfectly!
I recommend that every quilter get one of these! It iwll change your quilting life!