I have a Planet Bike 2W Blaze that is visible during the day in Superflash mode. Probably not super visible at noon on a sunny day, but I think it helps in the morning and evening, and on overcast days. I have a Planet Bike 0.5W Superflash tail light that it about the same story as far as daylight visibility goes. These are relatively affordable lights that do increase safety, IMO. If you have the money to spend, there are definitely brighter ones out there.