This is the Flat Four engine for your Tamiya SRB chassis, Sand Scorcher or Rough Rider. The purchase includes 2 versions of the engine. The Mk1 Engine included the gearbox covers with engine details designed in. The later Mk2 Engine has a simpler design where the Engine parts clip over the stock gearbox covers. Includes the complete the enigne plus your choice of exhaust, all exhaust styles included in this set work with both Mk1 and Mk2 engines.