Adjustable triangle - provides the features of a 45/90 adjustable triangle plus those of a protractor. angles from 0 to 90 can be drawn from the baseline with oe accuracy. Professionally precise - die-engraved graduations for high visibility and accuracy. Aluminum thumbscrew - the aluminum thumbscrew securely holds the selected angle and allows quick pickup and manipulation. High impact arcylic - made of high impact acrylic that is 0.100 inches thick and optically clear to eliminate parallax and allow close pencil tolerance. A Professional's choice our tools help bridge the gap between ideas and innovations. we are known for our wide selection of high quality tools at a fair price.