Keihin velocity stacks improve the air flow into the carburetors by smoothing small eddy currents that develop near the intake bells of carburetors, especially during high intake velocity conditions.  This not only increases horsepower by improving combustion, but also increases throttle response and fuel atomization.  Fits Keihin CR Special CR26-CR39 smoothbore carburetors.  Lengths are available in 45mm and 70mm for the CR26-CR33 carburetors and 45mm for the CR35-CR39 carburetors.  Includes clamps and additional replacement clamps can be purchased. 

Lengths are available in 45mm and 70mm.  Choose your length depending upon your clearances and tuning requirements.  Shorter lengths relate to less restriction and higher RPM power whereas the longer lengths smooth flow more and provide higher low RPM torque characteristics.  Velocity stacks are sold each.