Earl's O2 Sensor Weld Fittings are the ideal way to add a sensor when converting to EFI or adding a wideband Air/Fuel gauge for tuning carbureted engines. The weld fittings are available in steel or stainless steel to match your exhaust system. The thread size is 18mm x 1.5 and fit most OEM and aftermarket O2 sensors (GM, Ford, Chrysler & most import vehicles). Features are recessed step for easy installation by drilling a hole in the exhaust system and welding the fitting in place. Sold individually