RSX final drive for a MA gearbox with gear ratio of 12x68, 14x60, 13x60, 12x60. And contains the following updates / improvements over a standard final gear :

the end of the pinion shaft with both systems to close the 5th gear pinion, just the thread(earlier gearboxes) and clip(late gearboxes) type.
The second improvement are the two half moon machining to the inside of the crown wheel to lock it with 2 steel balls(supplied with the final drive) to the diff, this will save the cost of having to do it by the customer or to tig weld it, which is quite nice but it is a very hard and expensive job to do and especially to undo.