Westcott Adjustable Triangular Scale is made of clear transparent plastic. Westcott 10 Inch triangle ruler is adjustable which permits tracing of angles from 0 to 90. This drawing ruler has inner graduations on arc which give degrees of one angle while the outer row of figures gives the degrees of the complimentary angle. The transparent finish of these scales allow you to view through the page while you draw or work on an assignment. These clear rulers have 1/4 Inch, 1/2 Inch, 3/4 Inch, and 1 Inch circular openings for easy angle measurements. Westcott focuses on creating innovative designs that provide style and quality to an assortment of school, craft, and office products which are perfect for your drafting and drawing needs.