For the die hard sewist, who is frequently changing rotary blades, this 5 pack of genuine Olfa replacement blades is just what you need. Made of tungsten carbide steel, these blades ensure a quality cut with less effort on your part. The average rotary blade would dull quickly if used on any material other than fabric but with these Olfa 28mm blades you can easily move from paper to fabric without fear of dulling. For use with any Olfa 28mm rotary cutter.