Back caps: Back caps are used to apply pressure to the end of the collet. They are easily fastened by twisting into the back of the torch to keep the tungsten in place.
Collets: Generally made of copper, collets are used to hold the tungsten in place. They normally range from .020 to 0.25 inches in size.
Gas Lenses: These are used reduce turbulence when welding, and to increase shielding gas coverage.
Nozzles: Nozzles can range anywhere from 1/4 to 3/4 of an inch. Smaller nozzles will provide less gas coverage, while larger nozzles will provide more coverage.