45# steel main gear and 6061 aluminum differential case , it can be used directly For Arrma 1/10 Senton Granite Vorteks Bigrock 3S BLX & 550 Mega , 1/10 Kraton Outcast 4S BLX Series Replace code AR310872 , ARAC3711 , AR310886 Package include , 1x differantial kit , 1x main gear We have professional drivers and test engineers to help you solve your problems Fit for Arrma 1/10 Senton Granite Vorteks Bigrock 3S BLX & 550 Mega , 1/10 Kraton Outcast 4S BLX Series