The image on the display shows the adapter with the holding plate (2 screw holes). This plate can be removed, or they must not be used for fastening. The actual adapter is round. At the front of about 35 mm and the body is about 29 mm in diameter. The body has also included an M30 thread to a corresponding matching plastic nut. Therefore, you can attach the part solely on the central mounting and does not require the mounting plate.
In my desktop I drilled a 30mm hole with a Forstner bit. When power supply I use one of these power supplies for LED strip (12 volts). The there is also here at Amazon for small money. Only the plug you must then replace it with the two supplied clamps or solder the cable.
The rubber closure helps protect the device when not in use against dust.
