The GN1 valve cover is quickly becoming the #1 aluminum valve cover for the turbo V-6. Special Features of the GN1 Valve Cover: Precision thick wall aluminum alloy casting for even gasket compression and no Leaks! CNC machined for consistent fit. Clearance for roller rocker arms Unique spot-face and chamfer design breather bore accepts all popular breathers and maintains positive seal between breather and cover. No clearance problems. Bolts and washers included. Eye appealing and functional. A must for roller rocker installations.