This Edelbrock fuel pressure regulator #174121 is machined from aircraft quality aluminum for those who demand the best. This carbureted fuel pressure regulator has an internal diaphragm made of fluorosilicone to ensure high temperature protection resulting in an extended life. This Edelbrock fuel pressure regulator #174121 is compatible with all grades of gasoline, ethanol, methanol and E85 fuels. Pressure regulation slope is 0.75 psi/gal of flow rate change. Will hold fuel system pressure for at least 20 minutes after pump shutdown. Developed for optimum compatibility with Edelbrock electric fuel pumps.