These mild steel weld bungs are perfect for your tank project. For adding a gauge or probe, anything requiring a 3/8" female pipe thread.  These bungs are very low profile.                                                   Total thickness is .500"   Outside diameter is 1.00"  Flange thickness is .310"  insertion diameter is .875" You need to drill a 7/8" hole for it to fit before you weld it in place.                                                                                                                                                                                                                                                                                                                    We make these for a customer of ours and decided to sell some extras on E bay. Check our other listings for other sizes and types of weld bungs and tank fittings. We also make these in aluminum.                                                                           This listing is for 4 (FOUR) weld bung / fitting.