These ball-point gel pens have a Thermo-Sensitive ink formula that disappears with erasing friction on paper, that makes them great to use on fabric too! Not only do they write smoothly the ink will not smear, will not wash off, nor will it or rub off while you need it. But when you're ready the ink will magically disappear with the touch of a hot iron. Please always test pens on a sample of the fabric before use to be sure that the marks will completely disappear. May not be suitable for use with some dark fabrics or dyes fiber contents or fabric finishes. .07mm. Black ink. Un-Carded and sold individually from the box.