UltraMax ultra-sharp premium 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 Heavy-Duty LB blades. Long lasting durable snap-off blade - a new sharp edge with each snap. Blade container locks for safety. Fits most Heavy-Duty handles.