The most common gauge for a septum piercing is 16 gauge (1.2 mm) . However, it is also available in 18 gauge (1 mm) . Piercers may use a slightly larger needle (16 gauge) to make healing easier, as the larger hole allows for some swelling and prevents the healing from getting too tight as it heals. It is important to note that a good piercer will be able to look at an individuals anatomy and help determine what gauge of jewelry works best for them. If you dont remember which gauge your septum was pierced with, it is recommended to ask your piercer prior to buying any new jewelry because taking this measurement at home uses tools that you may not have.