Alvin 110PX mechanical drafting scale rulers. These 12" triangular scales are ideal for scholastic and vocational use. Satin finish, high-impact white plastic with tapered edges. Sharp, easy-to-read graduations resist wear. Mechanical drafting scales have the following graduations: 1/8, 1/4, 1/2, 1" to the foot; 1/4, 3/8, 1/2, 3/4 size; 50ths and 16ths.