Bestdotek&reg; boost bottles for baja 5B 5T 5SC, RC BOAT Zenoah CY RCMK Engine [1]Rovan Performance Bottle Kit Comes with everything needed to install. [2]Having 2 inlets on the manifold doubles the passageway for both the rising pressure of the cylinder, and the other inlet for the downward. [3]They will both work together to smooth out the incoming airflow and add a substantial amount of power rather than just one bottle alone. [4]While a single bottle kit is very effective, the Double bottle kits are demanded by the more savvy engine builders, and competition racers whom have upgrades their engines and are going for the "Elite" in horsepower, torque and RPM gains rather than just a recreational hobby enthusiast. [5] Fits HPI Baja, Rovan Baja and King Motor Baja and most 2 stroke gas engines 23cc to 30.5cc.