GENUINE FOR HONDA REAR MAIN CRANK OIL SEAL - K-SERIES K20A K20A2 K20Z VTECGenuine Honda rear crankshaft (main) oil seal. This is a direct replacement, Genuine Part for Honda K Series engines K20a, K20a2 and K20Z4. The rear main seal doesn't usually fail on these engines however it can happen, resulting in an oil leak into the gearbox bell housing. Rear main oil seals are often changed as preventative maintenance if installing a new clutch kit or undertaking other work which way involve the removal of the transmission.