The buttons can be switched around also. This model only has 3 buttons and 1 scroll. The right and left buttons for doing your normal Windows work. The scroll so you can scroll any Scrollbar just by moving it up and down on the mouse. The middle button is used for Click Lock, or can be configured to do anything you want.
Balls only get in the way.
Without balls it has a Class III Type laser detecting over 1,500 times every second to pinpoint accuracy. With my old mouse it used to be so much trouble. It was always sticking, and required cleaning almost every day. I went though almost 10 mice before finally trying this new Microsoft mouse. There was no copying any other brand.