The larger the number, the smaller the gauge of the body jewelry. A 0g needle is 5/16 inch and 8.25 mm. A 2g needle is 1/4 inch and 6.54 mm. To stretch a piercing from a 2g to a 0g is an increase in size of approximately 1/16 inch or 1.71 mm. This is a commonly performed stretch, as a 0g is the next larger size after a 2g.
The stretch from 2g to 0g is performed by a professional body piercer using a tool called a taper. Tapers are made of surgical stainless steel and look similar to body piercing needles with blunt rather than sharp ends. The piercer lubricates the thin end of the taper and inserts it into the piercing. As the client exhales, the piercer pushes the taper through in one swift movement, stretching the skin to the thickness of the taper's wide end. He then inserts the thicker jewelry.
There is an established belief among piercers and body modification practitioners that earlobes larger than the 2g to 0g range will not shrink back to their original size. If you are uncomfortable with the thought of your lobes being stretched for life, you may wish to stop stretching when you reach 2g. Earlobes stretched larger may require plastic surgery to repair. This surgery entails cutting away the bottom of the stretched lobe and suturing the skin back together.
Those who know they want their earlobes stretched to a 2g or 0g and wish to speed up the process may opt for initial large-gauge piercing. This is usually performed with a tool called a dermal punch, a tubular scalpel that excises a circle of skin. Dermal punch procedures are complicated and bloody, and as such they should never be performed by anyone other than a body piercer certified by the Association of Professional Piercers.