These fibre pens are suitable for any type of surface; the colours have extra covering powers and are super-imposable. Permanent on porous surfaces (stone, wood and rubber), ink can be washed off smooth surfaces, such as glass and mirrors with a damp cloth. The ink washes of skin easily, but may stain fabric and clothes. Non-toxic water based ink colours are light resistant and odour-free. Nibs are 4mm and ultra resistant and long lasting.