When held down, this button shifts all 20 functions to another set of programmed functions, for a total of 40 programmable functions.
What really sets the G600 apart is the "G-Shift" Button, which is a third button where you rest your ring finger. Other mice on the market can do this, though, and some of them are even wireless. You can even record delays between keys and clicks. The 12 highly tactile side buttons along with the other eight buttons can be programmed to any combination of keys and mouse functions using the Logitech Gaming Software included with the mouse. "logitech-g600" by Sinchen.Lin is licensed under CC BY 2.0