For All Oster Topaz, Sable, Rocker, Speed Line and Fast Feed Clippers Fits Models: 23-54, 30-31, 23-31, 56-31 23-51 The specially designed lower blade allows hair to flow into the cutting blades for fast and accurate cutting. The convenient adjustable blade feature allows you to quickly adjust from very close cutting to medium length, while saving you the added expense of extra blades Oster uses cryogenic technology to create the hardest blades ever. Cryogenic processing conditions metal to 300 degrees below zero, so molecules are aligned in a perfect structure. The result is a harder, denser metal that holds a sharper edge through prolonged usage. A5 Cryogen-X Blades also withstand more sharpening treatments for unsurpassed longevity. Sharper blades glide through coats with less effort, saving you and your clipper from unnecessary fatigue and wear. Cryogen-X Blades are manufactured from fine-grain, high-carbon steel that is cryogenically treated. With a Rockwell Hardness rating of 62, these durable blades were designed with the busy groomer in mind. Blades stay ultra cool for optimum durability.