Size: 30mm single hex (6pt). Designed for loosening and tightening brake caliper screws. When using in combination with a torque wrench, always use the correction factor formula that is etched on the wrench. Use with 3/4"D torque wrench. Manufactured from S45C steel (hardness HRC 38-42) with a black phosphate finish. Other sizes available: 21mm (Part No. 8538), 22mm (7340), 24mm (7341), 26mm (7342) and 27mm (7343).