This is a 6-piece mechanical set manufactured by Bahco, a leading Scandinavian manufacturer of hand tools. The set includes a 6M/6C spanner, which is designed for applications involving nuts, bolts, and screw heads of different sizes. The spanner has 6 metric and 6 imperial sizes ranging from 4 to 24 mm (1/4" to 1"). The set also includes a key set with interchangeable bits of 6/5/4.5/4 mm (1/4/3/16/5/32/1/8") sizes. The bits are made from high-grade and hardened steel with a satin finish for longer life. This set is ideal for use in automotive, machinery, electronics, industrial, and other repair and maintenance applications.