This listing is for a single 316L surgical steel push-pin flat back stud. Measurements: Post measures at 1/4 inch (6mm) length, with a 4mm disc on back. 18 GA (1mm). Approx. size of front piece is 3.1x7.7mm. Refer to listing images to get an idea of the size of the stud on-ear. Check your own ear measurement before ordering. Materials: This is a single push-pin, threadless flat back stud made from 316L surgical steel. Synthetic pearls. Care: These are tarnish-proof and waterproof, with proper care. If you come into contact with chlorine or salt water, cream, lotion, perfumes, etc., rinse in water and gently dry with a lint-free cloth. When not wearing, store in a dry, cool place. Avoid leaving this stud in extreme heat, as it can affect the finish. Another thing to note: these synthetic pearls h ave a slight grey undertone. This doesn't affect the function of these studs in any way.