I got this Noodler AHAB flex nib pen to practice line variations. Conventional fountain pens have a nib that writes a consistent width line, e.g, a FINE nib will write a fine line, a BROAD nib writes a wider broad line and so on. A flexible nib is pressure sensitive. The more pressure we press on the pen when writing, the wider line it writes and therefore creates letters of different width for a more artistic presentation. It does require a lot of practice.