With the Z Factor Perfect Putting Machine set up in the ARC mode you will be learning the muscle memory of an Inside-Square-Inside putting stroke. In other words, the putter travels INSIDE the target line on the backstroke, returns to SQUARE at impact, and travels back INSIDE the target line on the follow through. This stroke is thought by some instructors to be more natural and resembles a miniature golf swing. During this stroke the face of the putter opens relative to the target line, but remains square to the arc along which it is swinging. Most of the players on the PGA tour use some variety of this method.