Big Sucker™ Stage 1 air cleaners are engineered and proven to give your engine maximum airflow for more horsepower & torque. The patented hidden breather backing plate is o-ringed at the heads and exits inside the mouth of the throttle body for a virtually closed loop system, eliminating the need for any external hoses or hardware
Knuckle Stage 1 Air Cleaner Cover 
Increases Horsepower & Torque 
Patented Hidden Breather Technology 
Pre-Oiled & Synthetic High Performance Filters
One-Piece Aluminum Backing Plate 
Radius Air Inlet for Unobstructed Airflow  
California Air Resource Board: Executive Order D-639-10