This is an optional Arrma BLX and Roller Metal Differential Case, intended for use with Infraction, Kraton, Limitless, Mojave, Notorious, Outcast, Talion and Typhon 6S BLX kits. This Metal Diff Case set contains all the parts required to upgrade a plastic cased differential. Manufactured from lightweight, durable aluminum and hard wearing steel, this set adds strength and durability to the differentials of your model.