The Sewline Air Erasable Roller Ball Pen contains an advanced technology ink system with 0.8mm ceramic roller ball for fine sharp lines. The Sewline ink will disappear within 2-10 days from most fabrics. The ink marking can be immediately erased with water. It is advisable to remove any visible marks before ironing. Some fabrics contain sizing or other chemicals which may inhibit ink removal. Always test this Sewline pen on a fabric sample before marking up your project.