HP Billet Metering Block for racing and fine tuning applications. Our metering blocks are machined from solid billet aluminum and all circuits are threaded for tuning by changing the restriction size that is in the passage. There are 4 circuits to a metering block. The Idle, Main, Power valve, and Emulsion circuits. There are no ports/vacuum pipes on these metering blocks. They will come with a basic calibration to get you started, along with new gaskets.