But be sure to ask a professional seal engraver to carve by hand. Don't go to an engraving shop, a machine, a computer or a craftsman in a tourist attraction. Because calligraphy, painting and printing complement each other. If a painting and calligraphy is badly stamped, it will lower the grade of the whole painting and calligraphy. As for specifications, if your paintings and calligraphy works are generally within four feet, take 2CM. 2.5CM and 3CM are suitable. Should not exceed.