Inlet and outlet are -6 AN O-ring. Two inlets and one outlet. This is only for the red regulator (black regulator images are just for reference).
Universal 3/8" NPT EFI Fuel Injection Pressure Regulator Blue w/ Boost Ref Port
Universal EFI Fuel Pressure Regulator Kit 0-100psi with Gauge & 6AN Fitting - Ad
Universal EFI Fuel Pressure Regulator Kit with Gauge & Fittings
512-504-5 Boost Compensating Universal EFI Fuel Pressure Regulator
Adjustable Universal EFI Fuel Pressure Regulator Kit with 0-160psi PURPLE