Alumicolor"s solid aluminum drafting scales are the ultimate for accurate, professional use. Satin-smooth anodized aluminum scales are a pleasure to use. Alumicolor"s scales are truly professional with the full six scales on each one and ultra smooth, mark resistant surface.The Engineer scales have the following calibrations: 10, 20, 30, 40, 50, 60 parts to the inch.Each scale measures 12 in. in length.