Tamiya Planetary Gear Box Set Versatile system for reduction of high RPM electric motors for high-torque low RPM often used in precision instruments because of the reliability and accuracy of the unit precise, high-quality gearbox with a RE-260 motor built into the gear box itself Gear Ratios: 4:1 5:1 16:1 20:1 25:1 80:1 100:1 400:1