NorKut grinding discs are made with rugged NorZon grain so it cuts fast and lasts long. Resin bonded to a unique backing which resists cracking and breaking, these discs can be cut down to any size up to the 1" core. Use the cores to grind “pinch” welds and other hard to reach areas. Two quick change mandrels allow NorKut to be used on most popular tools. 7/16"-20 thread is for use with hand held pneumatic grinders while the 1/4" mandrel is for use on automotive drills.