https://www.amazon.com/Raphael-Kolinsky-Sable-Watercolor-Brush/dp/B001UN8UOY/ref=mp_s_a_1_4?crid=BAD93174Z6LA&keywords=rafael+8404&qid=1640376006&sprefix=rafael+8404%2Caps%2C902&sr=8-4
My favorite single brush