The Megasafe is an ergonomically designed heavy duty cutter that is made with an aluminum handle that allows both left and right handed users to easily perform general purpose cutting tasks. Unlike earlier versions of safety knives, the Megasafe features Martor's "smart knife technology" allowing the blade to automatically retract when the blade loses contact with the material being cut. The blade will STILL RETRACT even if the user leaves the slider in the forward position. This cutter features an easy, tool free blade change. This model comes standard with a 0.30 mm trapezoid blade. This blade is specifically designed for cutting corrugated materials with less resistance than the standard 0.63 mm blade. This will greatly reduce the risk of repetitive motion injuries associated with this task. (Replacement blade number 609.70) "GS - TESTED FOR SAFETY"