The Astro Tools RS516 50pc 5/16-18 Steel Rivet Studs are zinc-plated steel rivets with a #5/16-18 thread pitch. They have an outside diameter of 10.9mm and require an 11mm (7/16") drill hole. With a length of 16.5mm and an overall length of 30.5mm, these rivets are designed for heavy-duty fastening applications.