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, zinc plated finish, corrosion-resistant. Specification:Material: Carbon SteelFinish: Blue Zinc PlatedThread Size: M6 x 1mmOutter Diameter: 20mm / 0.8"Height: 6mm / 0.24"Package Content: 10 x Knurled Nuts