Copper Turbo Oil Feed Restrictor Fitting For Many Turbos, GT35, T25, T28, T3, T4, T6 AN4 Fitting Size to Oil Line M12 x1.0 Thread to Turbo Oil Fitting Has Built in Restrictor to Supply Proper Oil Pressure for the Turbo Which is Critical for Normal Turbo Operation. Without Correct Restrictor, Turbo Oil Seal Might be Blown and Leaking Oil.