Pair of 20x20x7mm megabass speakers, for DCC sound use. They are 8 ohms each so can be wired in parallel for the Loksound 4, 5 and Zimo decoders. These give a very crisp sound with lots of bass and are an ideal upgrade over the speakers which come with sound decoders or pre fitted to models. They fit most models where you can fit a standard 20x40 speaker