I just tried these for the first time this evening and they put out enough light to see the ground in front of you and plenty of light to be be seen by motorists. They stretch and clip on my handle bars and seat post very easily for a no headache installation. They are discrete so not likely to be noticed and stolen but cheap if they are stolen. I have no idea how long the batteries last. They are great to have as an emergency light if I get stuck on the trail. I put 5 of the CR2032 batteries in my emergency pack for spares.