These Philips lamps feature superior color quality and very crisp white light. Incredibly high 1.95 PPF (photosynthetic photon flux) per watt per second light source. 3,100°K Green Power or 4,200°K color temperature lamps available. High 92 CRI, 33,000 initial lumens (105Lm/W). High 90% lumen maintenance at 8,000 hr/High 85% maintenance at 20,000 hr. Double glass jacketed lamp is rated for either open fixture use (without glass lens) or enclosed fixture use (with glass lens).