Brush pens provide far more variation in line width than the usual fineliner pen. Their nibs have a large foundation that then tapers to some fine position. Normally the nib is made from a conical bit of felt, but there are actually pens that have a true brush tip made https://ink-drawing-for-beginners83692.creacionblog.com/36512682/how-to-draw-with-ink-pens-an-overview