Heavy duty .30cm high carbon knife steel Clamshell storage box for easy opening and closing Aluminium back for light weight and flexibility 100 blades with shelling paper for edge protection One third thicker than standard blades for rugged use American Line’s .012 Heavy Duty Single Edge Razor Blades are the highest quality high carbon steel blades made. Precision grinding yields a smooth clean edge to eliminate scratching surfaces during cleaning. American Line blades have been independently tested and proved to have the highest degree of initial sharpness for clean smooth cuts. The convenient clamshell storage box easily opens and closes securely for storage. Each blade has shelling paper for edge protection until you are ready to use the blade. Heavy duty blades are 1/3 thicker than standard blades for rugged applications.