Derby Professional Single Edge Razor Blades are ready to be installed on straight razors. Fits all straight razors. Derby Professional Single Edge Razor Blades are are perforated, hardened and ground by utilizing most advanced equipment. Cutting edges are deposited with Chromium-Ceramic, Tungsten and Platinum by advanced spluttering equipment for optimum edge strength promoting a longer shaving life. . From beginning to end, all Derby Razor Blades are subjected to severe quality control Inspection at every stage of manufacturing processes by unique quality control equipment. Each blade coated with a polymer for optimum comfort. . All Derby Razor Blades are Manufactured from stainless razor blade steel strip from Sweden or Japan. Each package includes 100 wax paper wrapped blades.