So basically, beginning on this side of the filament and ending on the other side of the filament, that is our A band. And notice that it actually also involves a portion of our thin filament because we have this overlap between the thin filament and our thick filament. So the A band is the region that contains all the thick filaments in their entire length. Notice that due to the overlap between the thin and thick filaments, the A band also includes a small portion of our thin filaments. So these small black regions here. Now, what about these Z lines?