Front & Rear Metal Diff BOOST BOXIntroduction Their all terrain toughness enables ARRMA vehicles to easily outlast other RC bashers. Exciting speeds are always possible right out of the box, but when you're ready to take your ARRMA 4X2 BOOST, MEGA, or 3S basher to even higher speeds with more powerful motors, ARRMA is ready with the extra durable ARRMA Metal Diff BOOST Box option part package. The ARRMA Metal Diff BOOST Box upgrades your model to 4S metal gear specs, giving it the