POP rivets (blind rivets) open end domed head, with a copper hat (head) and brass mandrel, are used to connect two pieces of material in a quick efficient way. Copper POP rivets with Copper Plated Steel mandrels are best for fastening copper or brass sheet where corrosion and decoration are important factors. Rivet diameter should match up with the size of the hole being filled. Grip range is the thickness of the material being fastened (installed length). Open End Dome Head Blind POP Rivets - 1/8" Diameter (#4) | Copper Hat, Copper Plated Mandrel. Often used to applications such as: gutters, roofing, flashing, leatherwork, residential building. commercial building products.