Lumen output is fantastic, however mounting fixture to mount can be cumbersome due to the small cavity where small screws and nuts are required for mounting. You may need a screwdriver tip to keep the nut from rotating for optimum tightness rest assured they will tighten.Specs state operating voltage is 9-30 volts; not accurate, maximum operating voltage is 20 volts. Mounted these on my ATV, fixtures illuminated with headlight switch. I did not know voltage regulator on my ATV was faulty until these fixtures burnt up immediately after raising engine RPMs. My regulator output measured 18.5 volts. (14 -14.5 volts is normal)I replaced the voltage regulator and purchased a second pair of these fixtures, all is well. Illumination is fantastic!Price is unbelievably amazing for these LED fixtures I would highly recommend….. just check your charging voltage prior to installation.Color temperature is between 5000 - 6000 Kelvn. White with a tinge of blue. You won’t be displeased. A remarkable improvement on any trail.