Mr. Gasket Flat Black Valve Cover Breathers are a fast, easy way to help customize your engine compartment with that stealth look. Engineered for high-performance street vehicles with positive crankcase ventilation and race cars with vacuum-balance systems, these push-on steel breathers with PCV fittings have 1-inch outside-diameter necks and 5/8-inch breather tubes and an integral metal baffle/foam element setup. Theyre designed specifically for small-block Chevys but fully compatible with all factory and aftermarket valve covers with a 1.250-inch hole.