Dixon dry erase markers write on all types of whiteboards and non-porous surfaces, including glass. Opaque inks flow smoothly and evenly on the surface. They wipe away cleanly and easily with a cloth or eraser. Wedge tips provide a variety of strokes. Vented caps conform to small parts specifications. AP certified, non-toxic. Each pack includes 4 markers in assorted colors. Sold as 3 sets for a total of 12 markers.