OLFA Stainless Steel Replacement Blades are meant to use with the OLFA Breakaway Steel Knife. The Breakaway steel knife allows graphic installers to continue to work through a dull blade by breaking off the tip to retrieve a new, sharp blade. Once the single blade runs out though, that means it's time for a refill. Get a 50 pack of stainless steel blades before you go to your next installation.