The shorter riser on these systems allows them to be used with EMI Silent Select systems as well as Mercury Silent Choice and other aftermarket selector systems. They also work well with Mercury "S" pipes. They are a direct replacement for stock Mercruiser manifolds in Bravo and Alpha applications where the exhaust outlets exit through the transom in the stock location. There is an additional charge on some late model EFI systems. Standard with black Fusioncoated finish. Optional finishes are available. Not recommended for use on engines equipped with long duration camshafts. System for Big Block Chevy.