Our patented RazorSafe System has grown and just got easier. Our simplified blade compatibility system easily ensures you are purchasing the correct blade sizes for your knives. Match the color on package or corresponding number on the blade to the blade holder for guaranteed compatibility. Blade compatibility codes correspond to blade lengths as follows: Code 500 are 5-inch blades, 350 3.5-inch blades, 301 3-inch utility blades, 300 3-inch blades, 250 2.5-inch blades, 220 2.2 -inch blades.