Kit comes with a rigid; lightweight; billet aluminum cage that provides a tight seal to the airbox and replaces your flimsy plastic stock cage. Twin Air PowerFlow Kit includes a pre-oiled Twin Air filter; a special aluminum cage and all necessary mounting hardware. Twin Air PowerFlow Kit for 4-Stroke models includes a rigid; lightweight; billet aluminum cage with a special backfire-resistant layer of foam laminated to the inside of the filter. Filter: Designed to increase airflow while ensuring the highest level of protection from dirt/dust Better breathing than competitors two piece foam design with proper density for maximum performance and filtration 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 More still air space in airbox for better breathing Exclusively formulated adhesive ensures glue seams will not break down Thick; flat foam; greaseless sealing ring ensures maximum contact with your airbox; while acting as a breathable gasket for increased air passage Large/flat sealing surface has a more reliable seal Fused outer and inner elements prevent dirt and grime from being lodged between layers - Trapped particles can restrict airflow and if dirt works it's way into your engine; a pinhead-sized granule will gouge your cylinder; piston and rings like a bullet 4-stroke models include backfire screen laminated to the inside of the filter Filter Cage: Billet aluminum construction Rigid & lightweight Replaces the flimsy plastic stock cage Provides a tight seal to the airbox Note: Some kits come with a plastic filter cage. Note: Images for reference only. Product may vary according to vehicle.