OLFA 18mm Heavy-Duty Ultra-Sharp Black Snap-Off Blades are the solution for tough projects when you need your utility knife blade to hold its own. Premium carbon tool steel provides durability. OLFA's dual honing process delivers a resilient sharp edge that is up to 25 Percent sharper than standard silver blades. Each blade is constructed with eight (8) segments per blade for plenty of accurate cutting action. Segments are etched with deep grooves for easy, clean breaks. When a segment is dull, a simple snap supplies a fresh, sharp edge. The universal 18mm size is compatible with most 18mm handles. Up to 25 percent sharper than standard blades. premium japanese tool steel. eight (8) segments per blade. fits most 18mm snap knives