Lightweight aluminum core is easy to shape and holds any curve firmly for accurate drawings. Graduated in both English and metric. Inch graduations in 16ths and 32nds are color coded black for quick identification. Metric graduations in mm and cm are color coded red. Convenient inking edges for pen and marker use and flat edges on both sides for pencil drawing. Lead and phthalate free. Blister-carded. 40".