The breather tube on the front driver's side of your engine block was designed to be connected by a hose to the intake system to facilitate Positive Crankcase Ventilation (PCV). If you change your carburetor or intake type and no longer have a place for the PCV hose, never block the PCV tube, and don't leave it without the protection of a filter. These filters are a proper fit for the PCV tube, and look great while protecting your engine! California residents: For off road use only.