✔ Material of Screws: Alloy Steel SCM435, high tensile, hardness: HRC 39-44 ✔ Material of Hex Key: chrome-vanadium steel, nickel plated ✔ Screw head style: button ✔ Screw drive style: internal hex, known as hex socket, hex Size 2.0 mm ✔ Rust proof: black oxide finish covered with anti-rust oil ✔ Easy to store: these screws and hex key come in a sturdy easy-use case [ Sizes ]----- [ Thread Length ]----[ Total Length ] M3 x 6-------6mm/0.24"--------7.6mm/0.30" M3 x 8-------8mm/0.31"--------9.6mm/0.38" M3 x 10-----10mm/0.39"-------11.6mm/0.46" M3 x 12-----12mm/0.47"-------13.6mm/0.54" M3 x 16-----16mm/0.63--------17.6mm/0.69" [ Package Contains ] M3 x6--------50 Pcs M3 x8--------50 Pcs M3 x10-------50 Pcs M3 x12-------50 Pcs M3 x16-------50 Pcs Hex Key ------1 Pcs About Internal Hex drives Internal Hex drives, also known as Hex Socket Drives, have a hexagonal hole in the center that requires an Allen key, also known as a hex key or Allen wrench About Button Head Button head is similar to standard pan head screws but have a curved top.