Contour Roller Mouse
You roll the roller and slide it left/right to control the pointer.
The 3 big buttons are left click, middle click, right click.
The 2 strip buttons are copy, paste.
The tiny button in middle changes mouse speed. Below it is scroll wheel.
Wrist Pronation Problem
With this, you don't have to “move hand off keyboard” anymore.
Depending on how much you type, moving hand off keyboard may be a good thing, because it provides your hand muscles a break.
One issue with this device is that you may get wrist pronation problem.
see Is Keyboard Tenting Important (Wrist Pronation)
The difference between the pro2 and free2 is that the free2 has a open roller bar, and detacheable wrist pad, and more precision (dpi). It's also about $40 more expensive.
thx to [2013-03-14 https://twitter.com/to1ne ]