Makita DK0060MX1 Corded/Cordless Combo Kit Automatic Speed Change technology adjusts speed and torque during operation for optimum performance Electronic RPM controller turns the motor off if rotation speed suddenly slows or wheel is forced to stop The Brushless Motor eliminates carbon brushes, enabling the BL Motor to run cooler and more efficiently for longer life; delivers 8,500 RPM Efficient BL Brushless motor is electronically controlled to optimize battery energy use for up to 50% longer run time per charge The electronically-controlled BL Brushless Motor efficiently uses energy to match torque and RPM to the changing demands of the application