Didn't read the other replies, but I will tell you what I do. I take wool yarn and wrap 20 wraps around 4 fingers of one hand. The wool I am using is fairly thin, so if you have thicker yarn you can get away using less turns. Then I take a piece of serving and wrap it tight around the middle, making like a figure eight of the wool. I put a drop of superglue on the knot to keep it tight together and when dry trim the ends. I put it between the strings where I want it and trim the ends so there is around and inch sticking out either side. You can go a little shorter, but if you go too short it is hard to keep it centered. Do the other end the same way, making sure that there are no loops that haven't been cut at the end. Go shoot some arrows and it will come out looking like a ball. If it is too big you can trim it some. I like the serving in the middle because you can move the wool puff a little bit to adjust the exact location without it all coming apart. Good luck.