Description: Material: Metal Differential Gear is made of Chromium Molybdenum Titanium to ensure longevity. providing higher strength and toughness to the gears and effectively eliminating the possibility of tooth sweeping.Enhanced Performance: RC Car Differential gear set has under treatment up to 55 degree to enhance its performance and make it wear resistant. It is a great upgrade for your RC car.Compatibility: Replacement Part is suitable for 8578/8579 RC cars original factory parts, providing a snug fit and improved performance.Easy to Install: RC Car Accessories can be easily replaced to upgrade parts for your model car and improve stability and overall performance.Replacement Parts: Spare Parts is a highly upgraded part for model cars, with a new look and superb workmanship. Specification: Material:Chromium Molybdenum Titanium Size Chart: 33T gear: 4.05cmx1.37cm/1.59inchx0.54inch, 13T gear: 1.95cmx1.25cm/0.77inchx0.49inch,1.87cmx2.85cm/0.74inchx1.12inch Package Includes: 1 Front and Rear Gear Set Note: 1. Please allow slightly error due to manual measurement.2. Due to the difference between different monitors, the picture may not reflect the actual color of the item.3. Wish you a wonderful online shopping!