Pressure/Vacuum Breather, Thread Size 3/8-18, Dia. Hex Flats (In.) 1 1/4 in, Height 2.16, Top Cap Dia. (In.) 1 3/8 in, Overall Length (In.) 2 5/32 in, PSI 3-6, Filter 20 Micron Bronze, Keeps Dirt from Entering, Vacuum (In. Hg) 2-3, Steel Body; Aluminum Top; Buna N Seal, Allow Sealed Pressure Systems to Vent Off Excess Pressure as Heat in System Builds up, Air Pressure is Allowed Back into System as System Cools