Male thread, "mushroom" style top design emergency vent made of heavy duty cast iron. Top acts as weather deflector and minimizes the chance of theft or vandalism. Machined top & base with Nitrile Rubber N "O" Ring provides a vapor tight seal. Available in 4", 6" and 8" with male NPT threads.
SCFH = Standard Cubic Feet Per Hour @ 2.5 psig