9&10. Select the tungsten diameter based on the thickness of the material you will be welding. A 1/16-inch tungsten is good for sheet metal up to about 1/8 inch. Then select a matching 1/16-inch collet and 1/16-inch collet body. Then install the correct size alumina cup, which directs the argon shield gas around the weld. If you were going to weld material that is 1/8 inch to 1/4 inch you would want to use the 3/32-inch tungsten. The type of tungsten is designated by the color of the tip. We got 2 percent thoriated tungsten which has a red tip for welding steel and green tip for aluminum.