What is described as a pressure-sensitive nib is a flexible nib that, through varying writing pressure, delivers variable line widths. Such nibs are mostly found in pre-war writing instruments, especially in Watermans up to about 1930; in modern series-produced fountain pens flexible nibs are practically no longer fitted, apart from a few Japanese exceptions like the Pilot Falcon or Nakaya, whose flexibility, however, often falls short of historical nibs. Anyone wanting to have a modern standard nib ground flexibly or have a stub grind worked in is best served by specialist nibmeisters such as John Mottishaw (nibs.com); he can regrind an M nib both narrower and more flexibly. Special editions like a 149 Special Anniversary should not, however, be used for this, since modifications affect collector value; regular series writing instruments are more suitable. The Music Nib is an alternative for line variation without flex behaviour.