The Artline 70 Permanent Marker is ideal for marking a variety of porous and non-porous surfaces including steel glass cardboard and wood. It has a bullet tip for controlling each stroke in art class at school. The markers have a bullet nib so you can attain a 1.5 mm line width. They are suitable for a variety of surfaces including cardboard wood steel and glass. These markers are xylene free for your peace of mind.