Norpro Oslo 5 Inch Utility Knife, Red 5 inch The blades are made of AISI 420J2 steel The blades are made by taper grinding and stone finishing, ensuring a perfectly smooth and indestructible surface. The Rockwell hardness of the blades is HRC 53 +/- 2 The handles are made of PP plastic which is a quality grade of plastic that ensures durability