proflow's new fuel pressure gauges come encompassed in a 40mm black coated stainless-steel body and feature brass 1/8 npt fittings. proper fuel pressure control is always critical for adjusting your carburetted or fuel injection system to achieve peak performance and that's why these gauges are all individually tested from the factory before being sold. they can withstand all regular unleaded fuels and alcohol-based fuels such as e85, making these great for all fuel systems. they are available with either a black or white face, and either come in liquid and non-liquid filled versions.