no2 is a legal Arganine Alpha Ketoglutarate (or something like that) supplement. It increases nitrogen retention and is a vaso-dialator. Dont expect any special synergy though.
I loved the pump from NO2, but again I was running it with Tren, 19-Nor, and also with a low carb diet, so I am not sure how much of it was associated with Tren and 19-Nor, but it seems as long as it isn't run with Ephederine, you should get a nice pump, as long as diet is in check.