the stock prop that comes witht the plane is a 11/5 it is the recomended prop for the OS46fxi, any prop from 11/4 to 11/7 would be ideal for the engine. when I first got my nextar I busted a few of the stock ones so I got some APC 11/5's there pretty good props for the NEXTAR.
I also ordered some stock ones from tower there pretty cheap at 1.99 and are the recomended ones for the plane http://www2.towerhobbies.com/cgi-bin...?&I=LXGAK9&P=M the red tips help with keeping a eye out for the prop arc.