This grunkan saved me from carpal tunnel syndrome a few years ago. I've used it ever since, and bought more.
It has three master finger buttons in width, which is gold in Pro / Engineer (Creo) that uses middle click diligently. It also has the thumb button and scroll wheel with "key".
Cons: it takes a while to learn to not move the mouse with your fingertips. If you make it happen to you pressing the buttons in season and out, and drag by mistake and drop things or activate icons not wanted.
And this first edition was strange in that the buttons were reversed - left click on the index finger, right click in the middle and ring finger button is "button 4". So I've mostly been using X.mouse Button Control for swapping middle and right. Later versions do not have this STUPIDITY.