CHROME STEEL REAR GEAR – 1PC 1. High grade chrome steel material degree of hardness of 50. 2. 13 tooth spiral gear made of high grade chrome steel. 3. When the quick start brake brakes, it does not damage. The car still run smoothly. 4. Only use with spiral main gear (STXM1200FR/G). Not compatible with stock low grade steel gears. Please for best race results use GPM parts only.