Alumicolor Ludwig Precision 18" Standard T-Square for Art Framing and Drafting, 82018 18-Inch length 1.5-inch wide x 1.66-Millimeter thick extruded aluminum blade High-quality plastic head is calibrated to 4 inches on each side of the blade Inch and Centimeter calibrations allow for flexible use in any situation Large printed numbers make for fast and easy to read Measurements