These refill leads are made with Premium Hi-Polymer? lead for strength and durability. They're also designed to produce smooth, uniform lines that you can count on as they won't smear easily. Compatible with almost all refillable mechanical pencils. Guaranteed to scan on standardized tests. Lead Degree (Hardness): HB; Lead Color: Black; Refill(s) For: For Most Refillable Mechanical Pencils; Lead Diameter: 0.5 mm.