This is a VERY BRIGHT LIGHT. It is absolutely great for on road riding as it is visible for quite a distance a quarter of a mile or so during DAYLIGHT hours. very good for night time rides as well. I'm very happy with this purchase and will purchase more for other bikes. Looks like it was designed by the fender manufacturer. Very good looking also.
I use this light as a 'backup' to my brighter blinky lights (eg. PDW Aether Demon, Danger Zone, etc.). While it is reasonably bright for dark paths and roads, it is overwhelmed by street lighting in urban areas. I like how it is screwed onto my fenders so it is unlikely to be stolen. The battery life is also excellent. Like I said, it is a reliable back up so that I never have to worry that I will be caught out on the road without lighting in the back.
My Spanninga fender light only has a continuoussteady output. For commuting in light traffic on shared-use streets, this light's flashing output was just what I was looking for. Compared to similarly priced seatpost mounted flashing tail lights, the output intensity is significantly lower. As opposed to seatpost mounted lights, fender mounting probably makes it impractical to steal, or losemisplace.
This light is probably not sufficient high speed or heavy traffic, and a brighter flashing tail light at helmet height could be a wise supplement.
If the light output was brighter, I'd give it 5 stars.