Along with the main shaft you must definately purchase this product as well. It fits perfectly with your yeah racing main drive shaft and decreases the friction between those two parts. One of the most important upgrades for your car is main shaft that gives the full power of your motor to all four wheels drive. If you are planning to upgrade your car with more than 3-4 aluminium parts for your chassis it would be better for you to buy the full upgrade kit from yeah racing witch contains aproximately all posible aluminium parts that exist separetely and if you calculate overall comes much much cheaper than buying one by one piece separete. Also if you dont want definately the blue colour, in free shipping options you will find the conversion car kit for tamiya tt-01, tt-01e, tt-01d etc, in red colour that comes in free shipping so you can save some money. This conversion kit contains metal ball bearing and oil damper and sure value great for money.