The num lock function is of any other keyboard are currently connected.The mechanical switch keypad can a fast response. Compare with the other standard keypad, the 21 extended some at the top, contain Esc,Tab,Back Space,and FN . 21 enhanced mechanical numberic keypad has 17 numeric and 4 additional ,including "tab""esc""??"and "FN". By simultaneously pressing the FN key and another key, you can input parentheses, an equal , symbols, or activate the calculator. Mechanical numberic keypad has 6 backlight brightness can be adjusted. By simultaneously pressing the FN key and another key, you can change the backlight and brightness. 21 mechanical numeric keypad is suitable for laptop users,banking, financial securities, business workers or Used with 87 keyboards, 82 keyboards, 68 keyboards, 61 keyboards and other keyboards without numeric section. Type: Blue Axis Colour: White Material: ABS+PBT Size: 12.3 x 8.2 x 4.2cm Package Contents: 1 x Digital Mechanical Keypad Only the above package content, other products are not included. Note: Light and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.