This video is about introducing Chinese calligraphy brushes. It covers the following questions:
--- Which type of hair should I choose to write different script styles? 写楷书行书隶书草书时我应该用哪种毛笔？
--- What size of brush should I use? 我应该用多大的笔？
--- How big should the characters be? 字应该写多大？

Amazon links to the brushes I bought:
Wolf hair: https://www.amazon.com/gp/product/B00...
Mixed hair: https://www.amazon.com/gp/product/B07...