1964-67 Chevelle/El Camino/Monte Carlo Small Block headers. 1 3/4, ..049 wall thickness, cnc mandrel bent primary tubes. CNC laser cut flanges, 3" slip fit collectors. These headers fit perfectly. Long tube design provides awesome low end torque and street performance. Recommended for use with ACCEL shorty header plugs. Sold less gaskets and fasteners. Mill finish."""