Brush pens offer a lot more variation in line width than the usual fineliner pen. Their nibs have a broad base that then tapers to your high-quality point. Ordinarily the nib is fabricated from a conical piece of felt, but you can find pens that have a true brush idea https://inkdrawingforbeginners14578.canariblogs.com/the-2-minute-rule-for-ink-pen-drawing-techniques-51572669