These Aluminum T-Squares from Alumicolor are made from the highest quality tempered extruded aluminum. The blades are aluminum and the heads are made from ABS plastic. The blade is calibrated in inches divided into 16ths on one side; the opposite side is calibrated in centimeters divided into millimeters. Calibrations are resistant to cleaners and solvents. Available in various lengths, T-Squares are indispensable drafting tools for drawing precise, straight lines.