Propeller Boss Cap Fins (PBCF) is a propeller enhancing device, which is designed to cut fuel consumption and exhaust gases by up to five percent while incurring no additional maintenance cost once installed. The unit, according to H. Yumoto Manager of PBCF Div. Mitsui O.S.K. Techno Trade, Ltd., is now operational on 720 ship worldwide. The PBCF rectifies the propeller hub vortex and recovers rotational energy otherwise lost in the propeller slip stream. Increasing propeller thrust by over one percent and reducing propeller torque by over three percent, the PBCF reportedly results in fuel savings of up to five percent or compared to vessels operating at equivalent speeds but without the PBCF, alternatively, a 1.5 percent increase in speed at the same engine output.