[sowise]

I don't remember what size it is sorry but I would recommend NOT using a 12 point socket if you are. You want a six point to match the nut, if you have the correct size socket and your nut is stripped from using a 12 point socket you may have to tap the 6 point down with a hammer, once flush use a breaker bar and cheater bar. Worst case scenario you match it up to the next size smaller standard or metric socket that just almost fits and whack it on with a hammer.

As long as your socket is still secure you should be good until the nut spins. Once you get a bit of a turn a typical impact should be able to remove it the rest of the way.

Also as suggested soak it in PB blaster or WD-40.