The Dcc Concepts Zen 218 decoder is a very versitile decoder which takes away the choice of which decoder to buy for your new locomotive as it comes complete with both 21 and 8 pin plugs. Due to its size will fit in most OO/HO scale locomotives.
This decoder also includes a seperate stay alive unit which will aid your locomotives running characteristics during slow running. This unit basically keeps the decoder "alive" for a few milliseconds if dirt or dead spots are located on the track.