What does 4H and 3B on a pencil stand for?

  “4H and 3B” represent the degree of hardness and softness of a pencil lead. The pencil with graphite as the main material can be used for drawing and writing. The hardness mark of graphite lead core is usually “H” for hard pencil, “B” for soft pencil, “HB” for soft pencil, and “F” for pencil…