Check the listing for details. 30 Pcs Round Head Button Studs 4mm Leather Punch Screwdriver, Gold. Condition: New. Listed at 10.76 USD. 1. The round stud size is 4mm and the length is 8.5mm/0.33"; the thread diameter is M3*0.5 and the length is 5mm/0.2".2. Alloy material, hard texture. The surface is electroplated, which makes it not easy to fade, improves its surface smoothness, and is beautiful and durable.3. Round head button stud is a commonly used fastener and is widely used in the clothing and leather goods manufacturing industries. It is often used for decoration and functional component connection of clothing, bags, shoes, and other products to ensure good fixation and visual beauty.4. The leather decoration kit comes with complete accessories. The set includes 30 round studs, 30 threads, 1 leather round punch, and a screwdriver to meet your different project needs.