This is the Hot Racing Heavy Duty gear set for the AR60 axle.  This is a direct replacement for the stock gear ratio (38/13)

Features:

• Offers improved gear mesh reducing slop in the drive train
• Spiral cut gears offer increased gear tooth contact and run quieter
• Hardened steel for increased strength and additional weight in the axle
• One set per axle required
• Laser etched markings