Universal coupling is available as an adapter from a motor chuck to a stirrer rod. For a 1/4" capacity chuck the universal coupling is available for 6 mm stirrer rods, 8 mm and 10 mm. For 1/2" capacity chucks the universal coupling is available for 18.25 mm and 19 mm glass stirrer rods. The coupling performs a number of functions. It is light weight and reduces the burden on the motor.