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 Power Flow kit comes with a rigid, lightweight, billet aluminium cage that provides a tight seal to the airbox and replaces your flimsy plastic stock cage. Includes a Fire-resistant Twin Air Filter. POWERFLOW KIT 150229C (includes Air Filter (FR), Aluminium Cage) HONDA CRF250R 20-21