The PMP Remanufactured Gilbarco Mechanically Calibrated HD Meter has a dial for manual calibration. The HD meter is different from the traditional Gilbarco meters in a few ways. The side covers are shaped to hold an O-ring in place instead of the traditional cork rubber gasket seal. The pistons and side cover have built-in stops to prevent excess travel. The internal valve and valve seat are composed of different materials.