OLFA-Art Knife Replacement Blades. This high-quality carbon tool steel is perfect for cutting paper, foam core, vinyl, film and more! This package contains twenty-five multi-purpose replacement blades for OLFA art knives AK-1 and AK-4 in one 2x1-1/2x1/2 inch container with one side for new blades and another for used blades. (KB, 9161) Made in Japan.