Logitech Marble® Mouse (904360-0403-EA)

I have 2 laptops, 3 desktops and I use this on every one of them. My hand never gets tired, I don't have Carpal Tunnel.  The only fatigue I get is from a heavy gaming night my thumb gets a little sore. I have had this unit dropped into a water footbath and after it dries out it's good as new. Not everyone can adapt to the ball on top, many friends don't like my mouse but I cannot use anything else. I can position my arm in any direction and still easily navigate, even with the mouse on my lap. they have not made any changes to this over the years and i do not use the scroll buttons so i cannot comment on their use.