This is a Staedtler slope ruler. I used it several times in university classes. There may be some minor scratches. Slope Triangle Ruler 25cm This versatile triangle ruler easily measures angles, slopes, and gradients. * Angles... All angles can be obtained using the Pythagorean theorem. * Slopes... Knowing the horizontal distance and the inclination angle, the slope distance can be found by multiplying the slope scale index by the horizontal distance. * Gradient... By multiplying the horizontal distance and the slope angle, the highest point up to an inclination angle of 45° can be found. Retail price: ¥5060 ● Material: Acrylic ● Thickness: 3mm