Brush pens offer more variation in line width than the usual fineliner pen. Their nibs have a wide base that then tapers to some great point. Generally the nib is made from a conical bit of felt, but you will find pens which have a real brush idea fabricated https://art-lover-australia98754.blogsumer.com/33544719/5-essential-elements-for-how-to-draw-with-ink-pens