The 21MTC adapter board is suitable if you want to digitize a locomotive without an interface, but do not want to freely wire the decoder. The adapter board provides a recording option for decoders with 21MTC interface. This decoder is simply plugged. On the other hand, 21 pads allow a clean wiring of your locomotive. This adapter board allows you to perform a clean conversion and take advantage of the additional features of the 21MTC interface (such as speaker outputs). Dimensions: Length 22.0mm x 17.0mm (With fixing tongue: 27.0mm x 17.0mm).