The device features four GameCube Controller ports on the front and is connected to the Wii or Wii U console with two USB cables. The black USB serves to power the adapter and transfer data, and the grey USB is used for rumble. Wavebird controllers can be used with this adapter, too. The adapter is available bundled with Super Smash Bros. for Wii U both either with just the adapter and the game but also with a copy of the game, the adapter and a black Smash-branded GameCube Controller. The adapter can also be purchased separately for £17.99/€19.99/$19.99.
An initial listing on the official Nintendo UK web-store mentioned that the device works on Wii and can be used for games supporting the Wii Classic Controller line and the Wii U Pro Controller but this seems to have been a mistake since it has been swiftly removed from the item description.