Review on Enhanced Comfort and Precision: Wireless Ergonomic Mouse for Right Hand (Medium) by Nathan Guzman

This mouse is not ergonomic because the thumb rest under the button is too curved. The natural position of the fingers is as if to the sides. The thumb brace forces the thumb to flex under the index finger, which keeps the inside of the thumb muscle in constant contraction mode. To make matters worse, the mouse is at an angle, so the index finger presses on the button instead of sliding down it. The thumb takes extra force to press it, so the index finger is over the button. This double strength makes my thumb ache quickly after using the mouse for a few days.