This tool set includes 7 industrial black Check Nut Wrenches along with a kit bag. Check Nut wrenches are drop forged from steel bar. These wrenches are available in fractional sizes from 1/2" through 1-11/16" and in Metric sizes from 10mm through 41mm. These wrenches are used on check nuts, stop nuts, jam nuts, and hydraulic fitting. The smaller sizes compliment service wrenches. (Also referred to as Thin Head Wrench) These are special purpose unusually thin head single end wrenches with a 15 degree angled slotted opening. They are generally used for servicing extremely thin adjusting and/or lock nuts.