Lifegard Replacement 40-Watt Ultraviolet Bulbs for QL-40, 80, 120, 160, 240 Its unique 4-pin connectordesign allows easy bulb replacement without shutting down the system End cap wire design drops bulb further into unit for maximum output, keeps heat away from sealing and allows easy replacement without shutting down Average Output: 15,910 Microwatt Seconds/cm squared