Self-Retracting Safety Utility Knife, Blade Dispensers with Blade Refills. Bi-metal Irwin blades stay sharp three times longer than ordinary blades and are unbreakable under normal working conditions. Smooth, durable, three-position slide exposes variable blade lengths, and stands up to frequent use. Optimized cutting angle for reduced hand fatigue. Push-button offers easy access to interior blade storage—holds up to five replacement blades. Blade Dispenser with Blade Refills. (Not shown.) Includes 50 blades.