Elfin Growth Hydroponic Metal Halide MH Conversion Grow Light Bulb/Lamp for Digital Ballast 600W Optimized spectrum and high PAR (Photosynthetic Active Radiation) to promote healthy plant growth. Lifetime: 20,000 hours/ 2.3 years. 600W:60000 Initial Lumens Extra-low lumen depreciation: maintaining over 90% of initial lumen output after running for 5,000 hours. The most reliable grow lamp on the market - 1 million+ happy users and counting.