16g 5/16" is the standard size that piercers initially use when performing medusa piercings. Once your piercing has had time to heal you may size it to 3/8" which is common for fully healed medusa piercings. This size creates a well-fitted look. If you are unsure your piercing is ready to size down or simply want to change your jewelry, visit us at any Platinum Ink location we are happy to help.