Just got one of these for my wife's bike. Great deal for less than £6.
Plenty good enough for on road use to be seen. Two would probably be ok for mountain bikes in the woods at night.
Fits standard 25.4mm bars, not the oversize ones.
3 Super bright white LEDs visible up to 2000ft Soft touch Power Switch accesses flashing + Steady modes Built-in QuickCam bracket mounts, adjusts or removes in seconds Up to 100 hrs run time on 3 AAA Batteries (included)
3 Super bright white LEDs visible up to 2000ft
Steady white LED
Flashing white LED
Special patent quick release bracket