QFX 3 Circuit Billet Metering Block 5 Emulsion - Fully Adjustable - Designed for QFX, and Holley® 4500 style carburetors. 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. Adjustable calibration for out of box performance - initially calibrated for most race carburetors. Simply add your jets to complete the installation. 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. Adjustable calibration for out of box performance - initially calibrated for most race carburetors. Simply add your jets to complete the installation.