Check the listing for details. RC4WD 4/1 Ultra Compact Gear Reduction Unit (540 Motor) [RC4ZU0012]. Condition: New. Listed at 22.99 USD. The RC4WD 4/1 Ultra Compact Gear Reduction Unit for 540 Motors is designed to fit any RC truck, car, robot, airplane or boat that uses standard 540 motor. It will work as long as there is enough room for the extra length (.7 inch / 18mm). Features: CNC machined high precision aluminum housing Stainless hardened steel micro size internal gears Custom made pinion gears Universal, fit any 540 Motor Engineered & Manufactured by RC4WD Specifications: Gear reduction ratio: 4:1 Overall diameter: 36mm Length: 18mm (.7 inch) Output Shaft OD: 0.12" / 3.2mm (with a flat surface for mounting standard RC pinion gears) Total metal gears: 6 Total Parts: 11 Includes: (1) RC4WD Ultra Compact GRU (1) Steel Pinion Gear Note: Due to the added length, you will need some longer motor mounting screws. For example on a Tamiya clod axle, you will need two M3 46mm long screws. About Us | View Store