i've bought this for my tamiya m-05, because required by "Tamiya (#54194) M-05 Ball Differential Set". it works smoothly, but i don't know if it 's better than the original. pretty sad that you need to buy this seperately from item 54194 and that tamiya didn't create a full package of both of them, you need them both anyways.
This upgrade parts is very essential for racing purpose. The universal shaft can perform constant speed while cornering even the steering at full turn. Besides, using this part can eliminate front tire "skipping" and vibrating that the dog bones normally do. A must upgrade for mini class racers.