From the manufacturer:
More abrasive than stumps, tortillons are excellent for rapid, thin blending on pencil, charcoal or pastel drawings. Comprised of rolled paper, these single-ended, spiral-wound tools are easily sharpened with a sandpaper block. Each package contains six tortillons. The assorted set includes two each of 3/16", 1/4" and 5/16" tortillons.