This is a unit circle made from 4 pieces of cardstock and a brad. The special right triangles rotate around the origin so that you can see the reference angle that you need for each of the angles listed on the circle. I used to make this unit circle with all of my trig classes, and I found that many students still had it the next year for calculus. I always make a few extra and stick them on the whiteboard with a magnet, and they get used constantly by my calculus students. It is hard to tell from the picture, but each special right triangle has all of its angle and side measures printed, and the red circle is about 7 inches in diameter.
You can buy a kit to make this circle for $12 at Facing Math. The kit includes directions for making the circle as well as two practice worksheets with trig ratios that are way better than what I found in my textbook. Cardstock and brads not included, but still worth every penny!