Volume 71 breaks down all shots in pool to six shots that come up over and over again. Its basically the overlap system that Mosconi shows in his book. They have just come up with different ways to package this material over the years. It basically works off the quarters system or three angle system if you already know that. Bert shows how the "in between angle" shots will still go in using the same aim point. This is possible because as you rotate around the OB the ball you see rotates. Bert doesn't number his shots like in SAM but the limits are all the same no matter what you want to call the system. The video is money well spent.