These adjustable protractors have two rotating blades that can be adjusted locked into place with a center nut to read exact angles from 0° to 360° to tolerances of 30 seconds or of 5/1,000’s. Popular uses include math, woodworking, and plumbing. They are made of a superior strength plastic that won’t break or crack with a lifetime warranty. They help produce angles more quickly and reduce related labor by 75%. There is also a 4” diameter attachable dial available with large, easy to read graduations that fits all models.