FUELAB® 535 Series Fuel Pressure Regulators have all the same great features as our 515 series, only smaller and weigh 50% less. They accept port style and non-port style union fittings without interference. Several configurations are available, supporting fuel injected applications up to 125 PSID. The 535 Series Fuel Pressure Regulator has a -6AN return port located on the bottom. Fuel Pressure Regulator Features. We carry all Fuelab products so if you can’t find what you need, please call.