This one little modification is such an upgrade for the TT-01 that it is as if the car has taken on a completely different personality. My car originally was a nasty hideously noisy car but the moment that I added these to all four corners the thing started to sound like an expertly tuned belt drive car. The units last forever. One thing I would warn about which is not the fault of the product so much as the sheer fault of physics. The pins that hold the units together are held in place by small allen screws. They sometimes back themselves out and if you are not careful you may find one disintegrate on you. What I would do is file a small notch (less than 1/2 of 1 mm deep) into the pin so that the allen screw has something to hold on to and also use thread lock (very small amount) on the allen screw when it is tightened down. It will allow the CVDs to last longer but nothing replaces the occasional rebuild of the CVDs which I would suggest one do every other month or so.