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."" Including Filter (FR) Aluminium Cage, Sealing Ring, 30mm Bolt, Mounting Hardware.