You can shoot the carbon arrows of any size through the aluminum biscuit but you can't shoot the aluminum arrows off the carbon biscuit. If you are in doubt, if I were you I would opt for the aluminum. The only problem you might encounter would be if you had to cant your bow to make a shot the arrow would be slightly off center. I personally would not cant my bow to make a shot,I would wait for a better shot angle, but I know some hunters that do and even practice for that shot.