K&N Performance Intake Kit for Opel / Vauxhall / Alfa RomeoThe K&N 57S 4902 Performance Airbox replaces the restrictive factory air filter and air box. K&N performance air boxes are designed to dramatically reduce air flow restriction as well as smooth and straighten air flow. This allows your engine to inhale a larger amount of air than the factory air filter assembly. More air means more usable power and acceleration throughout the engine's RPM range. The 57S 4902 Performance Airbox comes with a conical K&N