Billet Metering Block Kit (fits most 4779, and 4781 style carburetors). Designed to work with mechanical secondary carburetors that have 4-corner idle. Our billet aluminum metering blocks are machined to very strict tolerances then anodized for protection and good looks. CNC cut from premium aluminum and filled with precision parts, these blocks provide the ultimate platform for your performance carburetor. Standard calibration for out of box performance - designed to fit most real world street & strip carburetors. Simply add your jets and power valve to complete the installation. Includes the following items. 4-corner idle, must have correct throttle body and main body.