500mm - 19-1/2" Full-Flexible Steel Rule - mm & Inch Grads, mm & 1/2mm on One Side; Quick-Reading 10ths & Aircraft Quick-Reading 50ths on Rev. The Starrett 500mm - 19-1/2" Full-Flexible Steel Rule with Millimeter and Inch Graduation features a satin chrome finish. Graduations include mm and 1/2mm on one side; quick-reading 10ths (.10) and aircraft quick-reading 50ths (.02) on reverse. 500mm (19 1/2"), No. 34 Grad, Full-Flexible reverse.