Spectra Precision HR220 Laser Receiver Allows work indoors or outdoors to 250-feet Works in all horizontal and vertical applications, magnetically attaches on ceilings or metal studs, and includes a heavy duty rod clamp Front LCD and simultaneous rear corner LEDs (red above, green on-grade, and blue below) Auto shut off feature 30 minutes after last laser strike or button press 50-hour battery life Class 2 Laser	and &lt;1mW (less than 1 Milliwatts)