Milwaukee® ShockWave™ Impact Duty™ socket, impact rated: yes, measurement system: metric, hex drive, 3/4 in drive, deep socket, 21 mm socket, 3.54 in OAL, 6 points, forged steel, black. Milwaukee® 49-66-6396 ShockWave™ Impact Duty™ Socket, 3/4 in Hex Drive, 21 mm Deep Socket, 6 Points