Premium CR-MO Construction ➤Our 17mm, 19mm, 21mm 13/16-inch and 7/8-inch lug nut socket set is made of CR-MO (Chromium-Molybdenum) steel, build to handle 400–500 ft-lbs of torque. Compared to CR-V (Chromium-Vanadium) steel, these impact-grade sockets offer superior strength and 2 to 4 times longer service life – ideal for professional and DIY use.