Makita GA4542C SJSII High Power Angle Grinder, 4-1/2" Powerful 12.0 AMP motor delivers more output and variable (2,800 - 11,000) RPM SJSII provides a leaf spring and cam gear drive mechanism that is engineered to reduce vibration SJSII provides a mechanical gear drive to help prevent motor and gear damage by dampening the force on the gear when the wheel is forced to stop Variable speed control dial enables user to match the speed to the application Electronic Controller is a three-part electronic feature designed to provide the required power in high torque applications for increased tool life