I bought this for my TA05 that I'm building for top speed runs. Its supposed to reduce friction because there's only half the teeth in the pulley. I replaced both my front and rear diffs with this unit. One thing you have to look out for is this pulley uses 9 diff balls. The stock units only use 8. Thankfully Tamiya always give you a couple of balls extra when first building the kit, so if you decide to get this make sure you still have the extra diff balls. Can't tell if it makes a difference or not, the top speed or acceleration hasn't improved. But if it reduces wear and tear on my belts then its completely worth it.