Pro Marker - Sandstone This is Letraset\'s Pro Marker series of pens, they are double-ended with a broad chisel tip at one end and a fine bullet tip at the other. Pro Marker offer great value and top performance and produce colours which range from bright and vibrant to subtle pastel, they are high coverage, no streak and can be overlaid or blended. These are alcohol based, non toxic ink pens. The can be used on a multitude of surfaces including paper, metal, wood, glass, plastic and more.