The CSF Manifold is made from Billet Aluminum and 100% TIG Welded for strength, which allows it to be able to withstand higher boost pressures compared to the OEM plastic manifold. Aluminum has higher thermal conductivity than plastic resulting in a higher rate of heat transfer between the cylinder head and manifold. Adding the Thermal Rejection Spacer reduces heat transfer between the two metal components (cylinder head & manifold). The spacer absorbs the heat from the cylinder head and dissipates it rather than transferring it to the manifold. The CSF Thermal Rejection Competition Spacer was designed for vehicles competing in motorsports who demand the absolute best cooling in order to gain a competitive edge. However, including this spacer offers significant advantages to any vehicle.