combine with the ruler / office

This design is combine with the ruler, compass and scratch paper used together. It can make the hand-painted measurement more simple and easy, and more convenient to carry and store.
1. The measure of ruler is the standard length of 20cm.
2. The diameter of the circle is 1cm-40cm, and the size can be adjusted. Its accuracy can be achieved 0.1cm.
3. And it can record the data quickly.
4.adjust the radius of the circle,dialing the fixed bolt,then push down the button that can control the center of the circle so that you draw it precisely.