Plain finish one-piece aluminum backing plate. Used with OEM air cleaner cover with single central bolt or custom cover with central bolt with minimum ID 6-1/4" (159mm). The Big Sucker™ Stage I performance intake adds horsepower and torque. The patent-pending hidden breather system is O-ringed at the heads; passes through the backing plate and exits inside the mouth of the throttle body through proprietary shooter tubes.- Without cover - Takes all Arlen Ness Stage 1 air cleaner covers - Takes a custom round air cleaner cover with central mount hole; minimum ID 6-1/4" (159mm) - Increases horsepower and torque - With black pre-oiled air cleaner element - Aluminum filter top plate design eliminates internal mounting hardware.