SOLO line is our first generation product which was released in 2015, SOLO 600W COB LED Grow Light is the best cob light with highest PPF performance over 4'x4' on market, even up to now it still can beat quantum board lights and spydr grow bar light in ppf readings over 4'x4', for indoor grow tent, if you want the highest ppf output for your plants, then solo line is the only option for you.