Fantastic Electrostatic Headphones still unapproachable by almost anything on the market. One owner, non-smoking environment. Work perfectly. Headphones themselves are in excellent condition. The metal box has two holes on the side for mounting in a cabinet. The electrical plug must be connected to an AC power source. The front speaker/headphone switch should be left permanently in the headphone position as it is noisy. The original spade connectors have been replaced with top quality bayonets which attach to the speaker connector on your amplifier. The better the amp, the better the sound. The bayonets make it easy to switch between speakers and headphones if your amplifier doesn't have the facility to do it for you. Buyer is responsible for shipping and transaction charges.