Bosch Self-Leveling Rotary Laser Kit GRL 500 HCK AUTOMATIC: The Bosch GRL 500 HCK offers fully automatic dial-in grade with center line modes for automatic searching and positioning of the laser beam on receiver. It offers consistent leveling to 1650 feet. FAST-CHARGING: The integrated lithium-ion rechargeable batteries in both the laser unit and receiver offer extended operating time. Fast charge both the laser and receiver at the same time with a full charge within three hours. THEFT DETERENCE: The GRL 500 HCK locks when receiver is undocked from rotary laser while the alarm sounds if rotary is moved. The unit is also rendered inoperable without receiver giving the user piece of mind. TWO-IN-ONE: The Bosch GRL 500 HCK is both a remote control and receiver in one. All the information about rotary laser status, settings and measurements is easily accessible and in hand for easy one-person operation. Class IIa laser product, &lt;1mW power output Class IIa laser product, &lt;1mW power output