Arlen Ness Big Sucker 18-820 Stage 2 Red Filter Black Cover for 1999-2015 Harley Twin Cam Models One-piece aluminum backing plate features our patented hidden breather technology. Each hidden breather is o-ringed at the heads and exits at the mouth of the injector/crab to provide efficient engine breathing, eliminating the need for any external hoses or hardware Black Backing Plate and Cover with red K&N Filter Standard red filters are pre-oiled, washable and feature 4-layers of surgical grade cotton for optimum filtration and maximum airflow Radius air inlet provides maximum performance by providing unobstructed airflow