The back of this ear stud is 925 Sterling Silver Butterfly Push back ,( Post Length 10mm / 3/8" ) Lightweight, easy to take in and out yet stay securely in place And Comfy. Hypoallergenic, lead & nickel free Safe for sensitive ears. (comes with Extra Clear Silicone Bullet Clutch Ear Nuts for Extra Safety ) Little stored box. our products are always backed by a 100% Money Back No Questions Asked Guarantee