Uni-ball Power Tank Ballpoint Retractable & Fine Ballpoint Pens Refills-0.5mm-black Ink-value Set of 5(with Our Shop Original Description of Goods) 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