As the character "毛" literally means the hairs of an animal and is used in the word for 'brush,' a coat (animal) (in rare cases, chemical fibers) is usually used.; and the letters for fude are called Mohitsu (literally, a brush made of coat).
「毛」には通常は文字どおり毛(動物)（まれに化学繊維）が使われ、毛筆（もうひつ）という。