The fixtures run Samsung 301 B mid power chips - not a cob. These chips have been rated as highest luminous flux chip on the market - it equates in testing to 220 Lumens per watt - I use Lumens as it is easier to explain that luminous flux and with white light is a relevant number, although not definitive for horticulture lighting. We have found for running full cycles that 4000 K is by far the best white light spectrum available. If you veg / flower photos in different areas it is best to veg under 5000 K and flower under 3000 K - although we have professional grows that love the 4000 K as well for their veg areas, tends to grow a stronger "bushier" veg plant.