This well known speaker is probably the best speaker out there for OO gauge DCC sound. Its a large speaker measuring 65x29x14mm so isn't a direct fit for most models, but if you have the space (or can make the space by milling the cassis etc) then you wont be disappointed.
This speaker is aimed at more experienced modellers who have the tools and expertise to heavily modify a model to fit the speaker. For beginners please see my range of smaller speakers.
Includes the wire required to connect it to your decoder.