Heavy-Duty and Lightweight Utility Knife: Aluminum alloy and stainless steel construction with rust-free powder coating, durable yet lightweight at 0.7 oz, passing the 1.5m drop test. SK5 blades heat-treated to 1922°F achieve up to 64 Hrc hardness for long-lasting, extremely durable cuts on boxes, plastic packaging, and straps. Retractable with Auto-lock: Multiple locking grooves allow free control of blade length with precision. Automatically locks when releasing the button and easily retracts to lock safely within the metal frame when finished. Blade replacement is simple with the quick-release mechanism. Includes 10 extra blades.