All of Oster® blades are put through a 12 step process guaranteeing quality and craftsmanship. Oster starts with a fine-grain carbon steel that is heat treated to create a hard surface for greater wear resistance, leveraging a Rockwell Hardness Rating of 62. The patented Cryogen-X™ process takes the blades down to a -300 degrees for a deep freeze, producing a harder, sharper blade which extends the product life. Each blade is then hand lapped for a smooth cut finish. Includes 83AU top blade and 84AU bottom blade.