To protect the engine in very wet conditions, Twin Air designed a special Rain Coat (RC). The Rain Coat is an extra filter cover. During these extreme wet weather conditions, we advise to use the pre-oiled Twin Air filters, pre-oiled with Liquid Bio Power Filter Oil and on top of that mount the dry Rain Coat. RAIN COAT AIRFILTER HONDA CRF250R 22-24 CRF450R 21-24 CRF250RX 22-24 CRF450RX 21-24