The Arrma BLX GP5 42T Front Rear Diff Set is a set of differential gears designed for use with the Arrma BLX Felony and BLX Infraction kits. It is an upgrade or replacement part that can improve the performance and durability of your vehicle. The 42T differential gears provide increased torque and improved acceleration, making them ideal for high-power applications. When installed, these gears will help transfer the power generated by your motor more efficiently to the wheels, allowing your vehicle to reach higher speeds and tackle tough terrain with ease.