The Logitech MX Ergo "thumb ball" mouse. A normal mouse requires your entire arm to move to make the mouse operate properly. You might notice that the repetitive motion can cause muscle pain all the way from your shoulder blade, through your neck, down your arm to your wrist. A thumb ball requires just your thumb to move and makes life a lot easier on your arm. It takes two to three hours to transfer your motor memory skills from the standard mouse to the thumb ball and after that you're away to the races.