A4Tech hasn't gotten rid of the mouse cord, instead they've moved it from the mouse where it gets in the way, to the stationary mouse pad.
The mouse pad connects to your computer through a standard USB cable and gets its power from there. The pad then creates an electrical field that interacts with the internal circuitry inside the mouse and gives it power. As a result, the mouse must be used directly on its mouse pad.
There are many versions of the wireless battery free mouse that are catered towards different end users.
NB-20 - Mini mouse meant for portability for notebook computers. The pad contains a retractable USB cord.
NB-30/NB-35 - basic office mouse. Two normal buttons, and a single scroll wheel. The difference between the 30 and 35 versions is the way they look with the 35 having a more see-through body casing.
NB-50/NB-57 - adds two more buttons and zooming functionality.
NB-70/NB-90 - Both mice contain two scrollable wheels for vertical and horizontal movement. The NB-70 has five programmable buttons, while the NB-90 has six and the 2nd scroll wheel on the side of the mouse.
NB-80 - 8 programmable buttons and a more ergonomic shape.
NB-95 - 6 programmable buttons, and an easy access second scroll wheel that allows both wheels to be controlled by one index finger.
X-708K - meant for hardcore gamers features upgraded specs for improved performance.