Sunlite 30425-su f39t5/841/ho 39w fluorescent t5 mini bi-pin bulb, cool white the fluorescent 39 watt 4,100k cool white t5 high output high performance straight tube features a mini bi-pin base, provides a light output of 3,100 lumens at a color rendering index (cri) of 82 and can last an average of 20,000 hours. These lamp utilize a single and double coat phosphor system. Series lamps have an increased cri due to the use of tri-phosphors (rare earth phosphors). Tri-phosphors also increase the lumens/watt output of the lamp. These series lamps offer superior quality of lighting, increased energy efficiencies, and extend life.