Constructed from chrome vanadium steel, these wrenches have more certifications than a PhD candidate... ISO 1711 which specifies minimum values for Rockwell hardness and torsional strength for hand-operated wrenches and sockets, ISO 7738 which specifies the overall length and the maximum head thickness of combination wrenches, SAE AS954-E a certification covering strength, design clearances, and torque capacity, and there are more... but you get the idea. This all-encompassing collection of combination wrenches spans sizes from 6 to 22mm and lengths from 4 1/2" to 9 3/4" ensuring you have plenty of leverage when you need it. Includes sizes: 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22mm