Donaldson Torit Ex- Arm Weld Fume Extraction Arm The Ex-Arm effectively captures dust, fume, or smoke. The Ex-Arm is offered in dimensions of 4 in to 8 in diameters with lengths of 6.5 ft, 10 ft and 13 ft. The Ex-Arm is the easiest to position and requires the least maintenance of any arm on the market.