Vent Plug, 1 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 Top Cap Dia. (In.): 3-1/4 Thread Size: 1 NPT Overall Length (In.): 3-1/32 Height: 1-5/8 Country of Origin (subject to change): Taiwan