Flat Back Earrings Stud: Gauge size: 18G (1.0mm). Pin Length: 8mm Top size: 2.3~4mm. Comfortable size, suitable for most people. adopt a threadless push in design, easy to take on and off. Hypoallergenic and Nickel-free: Surgical Steel is comfortable for sensitive skin, Non-Toxic. You can wear it when sleeping or taking a shower, it will never corrode and turn green. Multiple Uses: Threadless push-in earrings can be used as labret studs, Monroe studs, lip rings, cartilage earrings, helix earrings, tragus stud, conch earrings etc. Wonderful Gift: A perfect gift idea for your friends and families , perfect for Anniversaries, Birthdays, Christmas, Valentine's Day etc. After sales service: Uni-J to ensure your complete satisfaction,90 days money back or exchange, If you have any size or quality questions, please feel free to contact us.