Russell Billet Aluminum EFI Y-Blocks are designed to route separate fuel hoses to each individual fuel rail for a balanced system. The inlet port is designed for direct connection to 3/8'' SAE quick-disconnect style hard lines. The ''Threaded Cap'' style EFI adapter fittings completely eliminate the plastic retaining clip and replace it with Russell's exclusive screw-in retaining cap for unsurpassed reliability. The dual O-ring seal insures a positive seal under high pressures. They are direct replacements for OEM fuel rail and return line fittings in late-model EFI pressure side application.