150mm - 6" Spring-Tempered Steel Rule with Millimeter & Inch Graduations, Graduations at 32nds and 1/2mm on One Side; 64ths & mm on Reverse. The Starrett 150mm - 6" Spring-Tempered Steel Rule with Millimeter and Inch Graduation features a satin chrome finish. Graduations at 32nds and 1/2mm on one side; 64ths and mm on reverse. 6" (150mm), No. 36 Grad.