you can do better for racing. Those would be good warm packs, or for the first or second heat. I'd get something more like this: http://www2.towerhobbies.com/cgi-bin...?&I=LXLYY6&P=7

I have one of these and the power is great in my BL setup! They are also pre-assembled which most sxs packs aren't. If you want a warm up pack that has a little more capacity and you can get it from tower go with this pack: http://www2.towerhobbies.com/cgi-bin...?&I=LXLWR4&P=7