The Staedtler Engineering Triangular Scale STD9871834BK is a 12" triangular scale designed for professional engineers. Made from high-impact polystyrene plastic, it features color-coded grooves for quick and accurate selection of scales. With three sides and six different scales, it includes die-engraved graduations that are easy to read and will not rub off. This fully divided scale offers measurements in 10, 20, 30, 40, 50, and 60 parts to the inch.