I would say about 10 feet each side, total about 20 feet. I don't know exactly, but it definitely hold less than the regular Honda head. But it is just so easy. Line up the arrow, stick the string through and cut so you get equal length, then just turn the head. You have to know how much to cut though. I wasted a few feet just the other day because it got full and I am too lazy to unwind the string as start over again. Winding the Honda head is a pain. It does not have a separator and I had to stick my index finger in between the two string to separate them during winding. Or else the string will bind and won't tap out.
I got the chart from here, I believe from Richard Martin, not 100% sure. So thank him, not me. I just have a habbit to safe things in case of future use.