2 Core American Inline Switch Black (UL Rated)
Width - 29mm
Designed not to be seen, this tiny little switch can only be used on Lamps that use 110v, i.e. Only to be used in USA. These cannot be used on 240v mains. Often purchased by people rewiring lamps to be taken back to the USA. They are UL rated, and so provide the customs with reassurance of electrical compatibly.
Before starting any electrical work, always switch off at the mains. If in doubt consult a competent electrician