HIGH QUALITYPlastic material, wear resistance, not easy to deform, and will not scratch your hands.LARGE NUMBERSClear large numbers design measurement; easy to read, suitable for blackboard, whiteboard, dry erase board, etc.EASY TO USEHollow center design, with detachable handle the teaching ruler is easy to grip.Size Chart90 Degree Ruler: 66x57x33cm/25.98x22.44x12.99inch; 45 Degree Ruler: 56x40cm/22.05x15.75inch; Protractor: 50cm/19.69inch; Compass: 43x41cm/16.93x16.14inch. You can choose 1/2/4pcs rulers as your needs.WIDE APPLICATIONMath geometry tool kit are essential tools for architects, engineers, artists, designers, teachers and so on. Appropriate big size to use for geometry drawing and math class, fits for classroom, school or office.