UltraMax® ultra-sharp premium Extra Heavy-Duty snap-off black blades, exclusively designed for maximum cutting performance, are ideal for applications where superior sharpness is required. These blades made from high quality carbon tool steel are developed using a "special" double honing process for extreme sharpness and are 25% sharper than our Extra Heavy-Duty HB blades. Long lasting durable snap-off blade - a new sharp edge with each snap. Blade container locks for safety. Fits most Extra Heavy-Duty handles. 7 cutting edges per blade. 20 blades per pack.