SHOCKWAVE� IMPACT DUTY steel (Chrome-Molybdenum) is high quality alloy steel which provides ultimate strength and durability. Best fitting thanks to 6 gripping points. Non-slip hex geometry to prevent socket and fastener rounding. Deep wall construction provides clearance for protruding bolts. Stamped and ink filled diameter markings and laser etched part number for wear resistance. Dual hole design and groove for security accessories.