Requiring no more than 10 minutes of handling, it is a tool perfectly suited to avoid "Mouse elbow" and other carpal tunnel syndromes, short it replaces a standard mouse.
Impec also to work on the train for those who do not like the touchpad.
So why only 4 stars you say?
Because I require and I found a little sensitive left click: right hand resting above naturally tends to trigger the click (at least for my hand to me), that I solved easily by removing the object and glisant a small thickness of foam under the key in question for the "cure" somewhat.