These are an essential upgrade for ANY standard TT01 owner. These feature a new gearbox cover with separate shock tower part which was introduced with the Tamiya TT01E design. Now you can benefit too from the much improved design!
I have seen gearbox covers break on standard TT01's - avoid this by getting these parts and fitting them to your TT01. As an added bonus you also get new front and rear uprights too (improved TT01E design) and new hexes - so this is a really useful upgrade at a good price!
Even if you are an existing TT01E owner, you should always carry one of these in your spares box just in-case.
You should note that although you can upgrade one at a time, you need two of these to do a full TT01E gearbox cover upgrade.