1/8 Inch MPT Steam Radiator Air Valve #40 from Hoffman / Bell & Gossett. This mini valve will balance the air accumulation in your heating system smoothly and evenly, with no hissing, clicking and banging. Heavy duty chrome steel construction: rust corrosion resistant. Features a neat, elegant and super dainty design, making it the ideal choice for tight spaces and decorative applications. Float type vent: installs in seconds: automates your venting no manual intervention required.