The freedom of a rueographic with the safety of a pen without ink exhaust problem: the metal ball of the air pen can move without friction when holding the angle pen The pen contains uni-box super ink, an ink with an advanced one formula that adheres to the fibers of the paper, does not attenu, is water resistant and does not contain acids a slight pressure results in a thinner line, a firmer pressure allows the ink to flow around the ball producing a more line gross