452F-40 single stage regulators are designed for medium to heavy duty gas welding, cutting, and heating applications. They are Harris Style regulators with a 2-3/4" diaphragm and a Victor style seat mechanism. 2" gauges for easy reading. Stem-type seat assembly for more reliable performance. Forge brass body. Chrome-plated housing cap for fuel gas and oxygen models. Self re-seating external pressure relief valve on oxygen, inert gas, CO2 and nitrogen models. Sintered bronze inlet filter. UL Listed.