Universal, Multi-Purpose Fitting, Female 3/8" -18NPT Mild Steel Weld Bung (1" OD), Female 3/8" -18NPT Mild Steel Weld Bung (1" OD), STEEL WELD BUNGS, Weld Bungs, Vibrant Performance female NPT bungs are available in both aluminum & mild steel and range from 1/8" to 1" thread sizes., 3/8"NPTFemMSWeldBung.