Description: Structure: The bicycle wheel part bicycle rear hub 85mm 20 hole features a sturdy structure with 4 bearings, including two drum hubs and two freewheelsSpecifications: It has PCD of 42/48mm, an OLD of 85mm, and an axle with an outer diameter of 10mm and inner diameter of 5mm. The axle is designed with internal threads for screw fixation or quick release rod fixationHole Count & Brake System: This product comes with a total of 20 holes suitable for round bent spokes with a diameter of only 2mm. It is compatible for C brake systemsFreewheel & Chain Requirements: The freewheel is 9T, hooking up to the third gear (3P). For optimal performance, it requires pairing with chains that are at least nine speed levelMaterial & Size: Made from aluminum alloy material for both the axle skin and center plus steel freewheel ensuring longevity and reliability in use. Please note that the package includes 1x drum hub along with two screws and nuts each for easy assemblyNote: Please ensure you have read through all specifications before purchasing to ensure compatibility with your bike model Specification: Material: Aluminum Alloy Size Chart: Length: 10 cm/3.94 inch Package Includes: 1 Rear Hub;2x M6 Screws2 Nuts Note: Please allow slightly errors 1-2cm differences due to manual measurement.