Mechanical Pencils, Lead Holders, and Refill Leads
Mechanical pencils come in a variety of sizes. The most common are the 0.3 mm through 0.9 mm sizes. These are very small leads that do not require sharpening.
The 2 mm and 3 mm sizes are comparable in size to the lead in a standard wood pencil and generally are sharpened using a lead pointer or sandpaper block.