Identi-Pens work on almost any surface! They have two permanent sharp points - a tough fiber fine point on one end and an extra fine plastic tip for details on the other. For use on metal, glass, fabric, photographs, plastic and wood! Non smearing, non fading and will not feather when it is dry! Waterproof and chemical proof. For best results spray with a matte varnish after using so that ink won't smear if varnish is brushed on. Note: when storing pens keep them flat and ensure that the caps are on tight.