Unlike others that use a metal-to-metal valve seat, the FX regulators feature a replaceable soft Teflon valve seat that helps retain fuel pressure longer after the car is shut down for easier re-starting. We even went to the trouble of adding an o-ring sealed spring hat to ensure no boost/vacuum leakage through the spring adjusting screw. FX-S Street version Fuel Pressure Regulator capableof flowing enough fuel for up to 800hp, and features four 1/8 in. NPT inlet ports and one 1/8 in. The compact size of the GFB FX regulators conceals a large flow capacity.