Chalkboard Drawing Instruments Durable, lightweight plastic instruments, designed for whiteboards/chalkboards. Triangles, protractor, and ruler are made of white polystyrene and feature handles for ease of use. Compass is made of clear acrylic, and accomodates most dry erase and magic markers Compass, with locking screw, rubber suction cup, 18 long, accommodates most dry erase, and magic markers. Radius 15. Qty :