Motive Gear Performance AX Series has 2 versions: Both are production lightened, both are for Ford 9 Inch rear ends.. One is a Pro Series gear set for big guns drag racing. It is made of 9310 steel. It is a metal that handles huge amounts of torque slammed into it on the starting line and comes back for more. It has all the features as the high performance series and it can have a Smith and Wesson Micro Polishing process done to it to decrease friction and extend life. Rotating weigh removed prior to heat treatment. The other High Performance AX version is made of 8620 steel, has all the make quality of the High Performance Series and has up to two pounds of rotating weight removed before heat treatment. Used in stock car racing, drag racing and is catching on in off road racing.