Type schematic (not to scale) of a MIG nozzle, labelled with the printed size and nozzle mount cited in the specifications below; this part's outside diameter, bore and length are not in our sources.
Bernard N1C34 MIG nozzle
Bernard N1C34 Nozzle 3/4", Copper, Slip-On: size 3/4 in, material Copper, nozzle mount Slip-On.