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 type of decoder is simply plugged onto the board. Solder tabs on the board are numbered 1 to10 and 12 to 22 to correspond to the pin out of a 21 pin decoder to make a clean wiring application of your loco possible.
 
 
Dimensions:
Overall Length – 24.0×16.0 mm
Without Mounting Tab – Length 19.0×17.0 mm