Arlen Ness Knuckle Stage 1 Big Sucker Air Cleaner Kit For Harley Unleash your engines full potential with the Big Sucker, crafted to maximize airflow and efficiency. This high-performance kit has been shown to achieve horsepower gains of up to 21, making it a must-have for riders seeking serious power. The hidden breather backing plate technology creates a clutter-free design by removing external hoses, while the water-resistant synthetic air filter offers easy maintenance and reliable performance you can count on. Features: Billet aluminum backing plate Integrated crankcase breather for a clean look Built in velocity stack for increased performance Synthetic filter element never needs oiling