The P/N 300-631 & 300-631BK Ultra Lo-Ram billet aluminum plenum tops are designed as part of the Holley LS Ultra Lo-Ram EFI intake manifold kits. It is commonly known billet is the best. The strength and rigidity of these components is impervious to cracking and further resists any vibration and harmonics. These 3D CNC machined pieces are cut from a solid block of billet and then anodized. Take your Ultra Lo-Ram to another lever with Holley billet components.