Alvin 106CB Tru-Angle adjustable drafting triangle provides the features of a 45/90 degree triangle plus those of a protractor. Angles from 0 to 90-degrees can be drawn from the baseline with 1/2-degree accuracy. Die-engraved graduations for high visibility. The aluminum thumbscrew securely holds the selected angle and allows quick pickup and manipulation. These adjustable triangles are made of high impact, 0.100" thick, optically clear acrylic plastic to eliminate parallax and allow close pencil tolerance. Alvin 6" adjustable drawing triangles with inking edge are made in the USA.