The ball diff comes standard with super hard steel diff rings, 7075 T6 aluminum diff shaft, carbide diff balls, hard o-ring for tighter adjustment, our specially designed 10 ball spur gear and lightweight 7075 aluminum shaft and diff parts.  The V4 diff now also comes with a molded spur and spur gear covers. The spur gear is super durable, quieter and much longer lasting.  The covers are now about 50% lighter than the aluminum variants, which gets the weight down to a scant 6.6g with covers and 5.8g without (including the left hub).