The best filter in the world can't do its job if there are leaks in the seal of the airbox. That's why Twin Air provides a complete line of products to ensure a leak-proof, fool proof fit. Twin Air's PowerFlow kit comes with a rigid, lightweight, billet aluminum cage that provides a tight seal to the airbox and replaces your flimsy plastic stock cage. A Twin Air Powerflow Kit includes a pre-oiled Twin Air filter, a special aluminum cage and all necessary mounting hardware. For Honda CRF 250 X (2004-2018), CRF 450 X (2005-2016).