The inner and outer ball cages (also known as constant velocity universal joints, CV joints) are important components in the transmission system, mainly used to transmit power and adapt to wheel steering and suspension movements.

Inner ball cage: connects the gearbox and transmission shaft, responsible for transmitting power and allowing the transmission shaft to expand and contract slightly (compensating for length changes)

Outer ball cage: connects the transmission shaft and the wheels, adapts to the angle changes when the wheels turn, and ensures smooth power transmission.