The 21 MTC adapter board is suitable for digitising a loco without interface and for the case you do not intend to wire the decoder freely.
 
The adapter board offers a possibility for installing a decoder with 21MTC connector. This decoder is simply plugged onto the board. At the other end, 21 annular rings make a clean wiring of your loco possible. A neat conversion can be made via this adapter board and enables you to use all additional functions of the 21MTC connector (e.g. loudspeaker outputs).
 
Dimensions:
Overall Length – 27.0×17.0 mm
Without Mounting Tab – Length 22.0×17.0 mm