P. G.wrote a review of Blackburn Mars 4.0 Rear Light on July 26, 2009
I previously used the Mars 3.0 at night and it was bright. I don't ride at night anymore but I picked up the 4.0 for daytime road riding. In daylight, the 1-watt LED is far brighter than the superbright LEDs of the 3.0 or other lights. Definitely a tool for daytime riders.