Fixed ratio 16mm diameter subminiature epicyclic geared motor mfa 941d621 this 16mm epicyclic sub miniature metal gearbox with 621 gear ratio is suitable for light industrial educational modelling and rd applications it has a high quality 3 pole motor with precious metal brushgear and has acetyl first stage gears for noise reduction the output shaft is 3mm diameter with a key flat mfa 941d621 sub min epicyclic gearboxmotor 621