The Carlyle 42-pc Master Hex Bit Socket Set by NAPA is manufactured with S2 steel, which is the highest-caliber metal available in professional tools today, ensuring maximum durability. Precision design bit tips provide tight fastener connection, and the surface of the socket contains a mirror finish with nickel-chrome plating for a smooth and comfortable grip. Bits are also coated with zinc phosphate to provide extra protection from rust. The master set features stubby hex, hex and long hex sockets in 1/4" and 3/8” drive sizes. Hex sizes are 1/8” to 3/8” and 4mm to 10mm.