The hole-unit on the XtendAlign Putting Aid comes with a regular-sized 4" hole, but the opening is merely 3". The reason for this is simple, but very effective! You practice making perfect putts into the center of the hole. Putting to the center of the hole gives you confidence that you will putt on line, every time! The putting line on the XtendAlign extends upto 16 feet! Now you can practice short and long putts alike without the hassle of major adjustments. This handy feature makes the XtendAlign a versatile and robust solution to your putting aid needs. The combination of the mirror and string provide instant feedback on your set up over the ball. By glancing back into the mirror to see the string and its reflection as one line on top of each other. This will ensure that your eye alignment is perfectly above the ball and the putting line, every time!