5.5mm x 2.1mm DC Female Jack connector. These are ideal for installing into Lemax models for connection to the 4.5v power supplies. Sits about 1mm proud of the rear panel. This is pre-wired for easy installation with the light(s). Specification: Black Part: Height: 13mm / 0.5"; Diameter: 14mm / 0.6" Plug Size: 2.1x5.5mm Pins: 3-Pin Panel Mounting Pre-wired with 20cm wire or if purchased with an LED can be pre-soldered to the Nano LED. Connector block included if not soldered to an LED