If you need to be precise, these pencils will get the job done.
Made from the highest quality graphite, pick from 20 distinct degrees of lead hardness depending on the project- from 9B (softest/darkest) to 9H (hardest/lightest) that covers the full range from light gray to black.
Prismacolor Turquoise Pencils use the HB Graphite Grading scale. The measure of "HB" falls right in the middle and most closely resembles a standard #2 pencil.
The "H" side stands for Hardness. The harder the lead (more clay is mixed into the core), the lighter the marks. Going up the "H" side- the higher the number with H, the lighter the shade that pencil will make.
The "B" side stands for Blackness. As you go down the "B" side- the higher the number with B, the darker your marks will be. Less clay is being added to the graphite inside the pencils, making the cores softer and darkening the shade.