Uni Ball Air 0.5mm Rollerball Blue, Green, Pink and Orange Barrel Black Ink Pack of 4 UBA 188E M

The revolutionary nib of the Air, unlike conventional rollerballs, is pressure sensitive, meaning that it gives a writing experience and differentiating line width similar to that of a fountain pen. Each pen contains black ink and has a 0.5mm tip that writes a slightly finer line than the medium. The Air pen contains Uni-Ball’s Super Ink which is not only water and light resistant "Tamper-Resistant", meaning that the ink cannot be washed off using chemicals and solutions used by people to fraudulently modify documents. When writing with less pressure you will receive a finer line as the ink is transferred by the ball itself, whereas pressing a little harder gives a thicker line as the ink is able to flow freely around the ball. Unlike other rollerballs, the Air features a ball which can move freely within a plastic surround, resulting in far less friction when the pen is held at the right angle.