SHOCKWAVE™ IMPACT DUTY steel (Chrome-Molybdenum) is high quality alloy steel which provides ultimate strength and durability. Best fitting due to 6 gripping points. Recessed corners allow torque to be transferred across the flats of the socket rather than producing stress on the points or corners. Thin wall construction provides access to tight spaces. Deep wall construction provides clearance for protruding bolts. Laser etched size markings for easy identification and won't wear off.