The center band is just another piece of acrylic left over from another pen. I drilled a 1/4" hole in the middle. I turn the pen with all three bushings. Once the pen is finished I take the center bushing out and replace it with the piece drilled earlier. The 1/4 inch is just the right size for the mandrel and the pen transmission. You then have fun shaping it to what ever you like. It is really quite easy.