The Olfa Automatic Self Retracting Safety Knife SK-8 is a heavy duty cutter with a spring blade the produces an audible click when it comes into contact with the material being cut. This ensures the blade automatically retracts the instant it loses contact with the material being cut. This will happen even when the blade slide is engaged and cannot be overridden for added safety. With an anti-slip, cushion grip this heavy duty knife is great for corrugate, packing materials and shrink wrap. The SK-8 cuts to a depth of 0.59"; 15mm.