The Angle Grinder has several safety features such as an Electric Brake which slows the disc to a stop almost immediately, Kickback Detection which detects sudden changes in wheel speed & will shut down the motor plus having an Anti-Restart function so the grinder will not start again automatically after shut off. Another great feature is the Automatic Torque Drive which automatically slows the RPM increasing the torque to power through the tougher cuts. A Built-in CPU gathers information from the battery's memory chip to determine optimum charging method & charges Makita Li-Ion 3.0Ah batteries in only 22 minutes & Li-Ion Compact series 1.3Ah batteries in only 15 minutes.