Set includes one brush pen and three black water-based dye ink refill cartridges. The famous Kuretake brush pens have fine nylon bristles perfect for creating strokes ranging from broad to super thin. Artists and calligraphers love Japanese brush pens because of their portability, convenience, and high quality. Ink cartridge refills and brush head replacements are available. The brush should optimally be used once a month, but if it dries, you can soak the tip in room temperature water overnight. Refill with a new cartridge after soaking. Bristles are smooth and springy. Extremely practical and controlable with a great snap-back of the hairs. Ideal for Inktober participants.