These versatile Staedtler Double-Ended Permanent Pens 18s will write and draw on almost any surface. The permanent ink is great for marking on wood, glass, acetate, rock and stone, both glazed and unglazed ceramic, and smooth concrete. So handy in the artroom, classroom and at home. These fibre-tipped marker pens are double ended with a broad 3mm nib on one end and a fine 0.5mm nib at the other end.