They can be used on ALL Nintendo Wii Game consoles. They are universal regardless of where your console is from.
The Nunchuk builds on the simplicity of the Wii Remote and goes an extra step to meet the needs of specific types of games. The Nunchuk connects to the Wii Remote at its expansion port and is used in conjunction with the Wii Remote.
Along with the analog stick, the motion-sensing Nunchuk also contains two buttons positioned for quick access. Because the Wii Remote and Nunchuk are only relatively dependent on each other, players are free to hold them in whichever hand is most comfortable.