It is absolutely must have for those who bought TT-01 !! Don't think about alu suspensions. Firstly you need to remove this plastic shaft which can't forward the force to your differs and then to wheels. After tune up by this parts car is more sensitive for acceleration and whole behavior is much better than on the begining. Moreover standard shaft has a little disadvantage, it was loose and in high motor speeds vibrate a lot. After installing this problem disapeared. I am very proud that original part cost is so atractive concerning other manufectarurs. Summarize if you want to tune TT-01 you MUST buy alu shaft!!