Vent Plug, 3/4 NPT, 1-5/8 In Price For: Each Item: Vent Plug Application: 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 Type: Relief/Filler Overall Length (In.): 2-13/16 Height: 1-5/8 Top Cap Dia. (In.): 3-1/4 Thread Size: 3/4 NPT Country of Origin (subject to change): Taiwan