1.Thin type knurled thumb nuts. This is a carbon steel knurled nut. 2.The circular nut with knurled is easy to assemble and disassemble.3.Made of good quality carbon steel material, nickel plated finished, wear-resisting and durable to use. Specification:Material: Carbon SteelFinish: Nickel PlatedThread Size: M4 x 0.7mmOutter Diameter: 12mm / 0.47"Height: 4mm / 0.16"Package Content: 20 x Knurled Nuts