The hardness mark of lead pencil is usually "H" for hard pencil, "B" for soft pencil, "HB" for moderate hardness pencil, "F" for hardness between HB and H pencil.
Arrangement (from soft to hard) 9B, 8B, 7B, 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H, 10H and other hardness grades.
The higher the number before the H, the harder and lighter the lead. The higher the number before B, the softer and darker the lead. Pencil leads are classified according to the amount of graphite in the lead. H type pencils, the hardness of the core is relatively high, suitable for the interface of relatively hard or clear objects, such as woodworking drawing, field drawing, etc. HB pencil core hardness is moderate, suitable for general writing, or contouring; B type pencils, with relatively soft leads, are suitable for drawing and can also be used to fill in some machine-readable cards. For example, we often use 2B pencils to fill in answer sheets. In addition, there are common colored pencil poles, that is, people often say color pencils, mainly used for drawing.