Edelbrock part #7225 Intake Gaskets fit 1958-1979 361-383-400 B and 413-426-440 RB Chrysler Big-Block engines allowing for optimum flow (port fit) and sealing performance. MP-2N Micropore technology material is tough and heat resistant, yet has great compressibility and recovery. This means that when compressed, the gasket will conform to any imperfections on the sealing surface even with low flange pressure. Good recovery help keep the seal through thousands of heat cycles. A nitrile bead around each port opening adds a touch of compression where it is needed the most. Impervious to fuel, oil and coolant, this synthetic fiber composite is ideal for your performance engine build.