Quick Change Retractable Utility Knife. 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. Quick change mechanism lets you easily change, remove and reverse blades without opening the knife.