Twin Air 150212FRx Pre-Oiled Backfire Resistant Replacement Air Filter Fits: Honda CRF250R 04-05, CRF 250X 04-13, CRF450X 05-13 Pre-oiled air filter with a special backfire-resistant layer of foam laminated to the inside of the filter Dual foam design: Coarse open-pore foam catches airborne dirt, grime and sand, fine open-pore inner foam acts as a second filter to trap the smallest particles while ensuring maximum air passage Thick, flat foam, greaseless sealing ring ensures maximum contact with your air box, while acting as a breathable gasket for increased air passage Fused outer and inner elements prevent dirt and grime from being lodged between layers while the exclusively formulated adhesive ensures glue seams will not break down