The most significant functional difference of brush pens from felt-tip pens is the far greater compliance of the tip. Brush pens are an obvious alternative to ink brushes for Chinese calligraphy and Japanese calligraphy, but are now also commonly used in other forms of calligraphy and by artists such as illustrators and cartoonists. The primary appeal of these pens to such artists is that they allow a great deal of line width variation in response to small changes in applied pressure.