The OLFA RB28-5 replacement blades are for 28 mm rotary cutters used in quilting, sewing, and craft cutting when you need tight curves and detail work. This set includes five tungsten steel rotary blades for detailed cuts and is for use with the OLFA RTY-1/C, packed in a storage case for safer handling. Keep blades in the case between uses, install carefully to avoid chips, and change blades when the cut edge starts to fray.