What is the general diameter of writing brush used in seal script?

from a professional point of view, it is generally recommended to use a wool brush with a caliber of **.8-1cm** when writing Xiao Zhuan (whether Qin Zhuan or Han Zhuan). Such a brush with a caliber and a sharp edge (with a sharp edge of about 5.8cm) is suitable for showing the charm and brushwork of Xiao Zhuan. Of course, this is only a suggestion, and the actual choice depends on personal writing habits and styles.