Turblown Engineering designed this 6061 billet aluminum 5/8 Barb Oil Drain Flange for their EFR 347ss investement cast manifold turbo kits. The oil drain flange is designed with a rubber o-ring to prevent any leaks along with an extended barb to help with the clearance of the turbocharger/manifold. These are bolt on for all EFR turbochargers, and the S6 FD front cover. These will not fit the FC3S front cover. 0.500" inside diameter.