OUR S-SERIES BRAKE HOSE HAS A COPPER WASHER BETWEEN THE BANJO AND THE HOSE. IF THIS WASHER IS MISSING, IT MAY CAUSE OIL LEAKAGE. THEREFORE, PLEASE REMIND TO ENSURE THAT THE COPPER WASHER IS NOT MISPLACED DURING INSTALLATION. WE HAVE INCLUDED AN ADDITIONAL SPARE WASHER INSIDE A TRANSPARENT BAG IN THE BOX.