The Eaton Fuller Square Key, part number 21303, is a genuine OEM manual transmission component used in Eaton Fuller gearbox assemblies. Square keys are precision-cut drive components that lock gears, hubs, or shafts in rotational alignment, preventing slippage under load. This part is sold individually (each). If you are building up a transmission or replacing a worn or damaged key during a gear or shaft service, having the correct OEM square key on hand keeps the job straight. Pro Gear and Transmission carries genuine Eaton Fuller components. Call us to confirm this is the right key for your specific build.Interchanges:HF21303FeaturesGenuine Eaton Fuller OEM part number 21303Square key design for gear, hub, or shaft rotational alignmentSold individually – unit of measure: eachCompatible with Eaton Fuller manual transmission applicationsTech SpecsPart Number: 21303Part Type: Square KeyUnit of Measure: EachApplication: Eaton Fuller Manual Transmission