The front bar on an ex is 27.2mm just like the ST bar, only difference is that it's hollow and has rubber endlinks. All you do is buy some poly endlinks from energy suspension. This set-up allows you have some oversteer, kick the ass out in a corner, which for autocrossing and for fun is much better. People with the Front bar say you get too much understeer,which is when the front just plows ahead and doesn't turn. Some people still like this, but if you have an EX it's pretty well accepted to just go for the rear.