The most common gauge used for nipple piercings is 14 gauge (14G), followed by 16 gauge (16G) and 12 gauge (12G) . However, the gauge used for the piercing may depend on the size of the nipple. It is important to choose the correct gauge size to ensure a comfortable fit and avoid accidentally shrinking the piercing channel. The length of the barbell used will depend on the size of the nipple and the piercers preferences, and it can be anywhere from 3/8-inch to 1/2-inch long. The initial jewelry will need to be long enough to accommodate swelling, and after healing, you can switch to a different style if you prefer.