Great, bright light with variety of flash modes. Unfortunately the bracket is not big enough to fit my seat tube on my road bike. The bracket fits my mountain bike however which has a thinner seat tube.
I worked around the problem by buying some 200mm black cable ties and used these to fix the light to my seat post using the belt type clip that comes in the pack. After an 18 mile jaunt at speed it was completely secure. UPDATE: have now done about 200 miles with the light attached using cable ties and it has not loosened and functions well.
This is a cheap but very bright light although shipment from Hong Kong did take a few weeks. January 2014 Update: The light got wet from rear wheel spray, not rain. This stopped it working. I dried it out and the batteries, it will turn to permanent setting only when the batteries are inserted and will turn off only when they are removed; the on/off/cycle mode button clearly no longer functions. So, after 750 miles it's no longer of use and if I had one again I would never let it get even remotely damp as it is not a hardy product. Cheap though, but not to be used if there is a risk of surface spray or rain.