An HB pencil is a type of pencil that falls in the middle of the graphite grading scale, which measures the hardness of a pencils graphite core. The HB scale is commonly used outside of the United States and measures the ratio of graphite and clay in the core. An HB pencil is balanced between clay and graphite and typically serves as the equivalent of a No. 2 pencil in the United States. The higher the number on the scale, the harder the writing core and the lighter the mark left on the paper. As the pencil core becomes softer, it leaves a darker mark as it deposits more graphite material on the paper. Softer pencils will dull faster than harder leads and require more frequent sharpening.