Welding Nozzle. Solid Copper Slip on styleGas Shield Welding Nozzles for Tweco / Lincoln #3 #4 style Mig welding gunsUse these nozzles with #34A nozzle insulator. Two (2) nozzles per pack. Select the nozzle for you application from our list. Welding nozzle for Tweco style Mig guns ship the next business day.