Uni-ball Power Tank Ballpoint Retractable & Fine Ballpoint Pen Rubber Grip Type-0.7mm-black Ink-value Set of 10 Ink is always pushed out by the pressure of air Ideal for the outdoors or the work which stands and comes out, since it can write also upward It is suitable also for writing to a calendar. Even if it writes quickly, it is stabilized and ink is pushed out. Writes on wet paper, upside-down, in temperatures down to -20 C