... S2 (hardness) 2, good quality 3, professional Insert screwdriver bit setManufacture and supply various full series of screwdriver bits, nutsetters ... , nut drivers, sockets, socket adapters, bit holders and quick changeconnectors for screwdriver bitsmaterial types:Cr-V ... Cr-coating, Zn-coatingHead types:PH, PZ, slot, Torx, square, hex, hex-plus, Z-spanner, Torx hollow, Torx plus, ...