The 3 Pcs 1/2″ Dr. Deep Impact Socket Set (17-19-21mm) is designed for heavy-duty fastening and loosening tasks using impact wrenches. Made from high-strength Cr-Mo (Chrome Molybdenum) steel, these deep sockets provide excellent durability and resistance under high torque applications. With a 78mm length, they are ideal for reaching deep bolts and nuts in automotive and industrial work.