These are straight drop in replacement dog bones for the TT-01, useful if you bash (and crash) and want them to be as durable as possible. However, for racing (and more skilled drivers) these are not quite as useful because although they flex less than the stock plastic, they are made out of steel so they are VERY heavy. Know what you want out of your car before you buy parts for it. Can't be beat on the price, makes great replacement parts if your TT-01 has suffered a lot.