My Serfas True 500+ (500 lumens, not surprisingly) is very visible in daylight on flashing mode. The mount is excellent and cheap to replace, by the way. I'm not sure what minimum lumen rating you should be looking for. If you're mainly concerned with dawn, dusk, and gloomy days, then 200 is probably plenty. If you mean high noon on a sunny day, you're probably going to want more.