These hi-flow fuel rails are a direct fit and work with the factory intake manifold and injectors. They feature 5/8" diameter fuel passages for more flow capacity. Construction is black anodized aluminum with laser etched Holley EFI logo for long lasting good looks. Four (4) -6 AN to 3/4-16" O-ring adapter fittings are included and if desired, the rails are machined to accept -8 AN (3/4-16) fittings (available separately). Each rail has a 1/8" NPT port for installation of a fuel gauge. Mounting hardware is included, with bolt spacers to allow for both tall or short style injectors.