ThunderJet for S&S E/B Carburetors, Black Fits all S&S 'E' or 'B' Carburetors Most cost effective horsepower per dollar you can buy! ThunderJet is an additional high speed fuel circuit, delivering needed fuel to the engine at higher rpms, 4500 & up. Use the main jet to tune for smooth, broad mid-range power and supplement the top-end with the ThunderJet Join thousands of satisfied customers worldwide!