150 mm Grooved Drafting Protractor
This is a 150 mm half-circle drafting protractor, 3.2 mm thick. Angle ticks are cut into the top every 5°, with longer ticks every 10° and the longest at 0/45/90/135/180°. It also has a 140 mm ruler along the base and an M3 clearance hole (3.4 mm) at the vertex, so you can mark the centre point or pin it down with an M3 screw and swing it. Two open windows let you see the drawing underneath, and the whole part uses about 20 cm³ of plastic.
desk protractor drafting stationery