Andis UltraEdge Clipper Blades are made from high-carbon steel and processed through a unique carburizing heat treatment that actually adds carbon to the existing metal producing a harder cutting surface. Blades hold a razor sharp edge that will endure prolonged use and more sharpening treatments. Each Andis UltraEdge Clipper Blade is sharpened to exact quality standards and is hand tested before it is shipped. Blades have a Rockwell Hardness rating of 65.