A great add on to The Perfect Putter. This 5mW 532nm green laser allows you to know where the device is aligned in seconds. It gives you the ability to trace the line up and down all the way to the hole without the necessity of having a backboard and it works great outside on bright sunny days. It attaches to the back stand making it really easy to put it in and out. It comes with a 16340 3.7v rechargeable Li-ion battery and a charger.