This wrench design is ideal for hard to reach areas, such as the mounting or dismounting parts in an automobile engine or in machinery. Steel alloy with high quality molybdenum-vanadium and controlled heat treatment to provide the best endurance. 3-PIECE SET This wrench design is ideal for hard to reach areas, such as the mounting or dismounting parts in an automobile engine or in machinery. Steel alloy with high quality molybdenum1vanadium and controlled heat treatment to provide the best endurance. 31PIECE SET.