Jasper Circle Cutting Jigs
 

These are good jigs. However, when you use the small one on circles
smaller than a couple inches, be sure you push the pivot pin down far
enough so that the collet of the router doesn't hit it when you plunge.
If it does hit it, the jig may shatter and send the pin zinging across
the shop at a reasonably high rate of speed. By this point I'm sure
you know how I know this.
Safe routing.
JP