This item is a good little thing for you bike, although it does not make the whole wheel light up with the circular glow as the description and image indicate, it does create a bright little light which draws the attraction and attention of those other road users, namely the pesky cars who don't know how to check mirrors or observe for the bikers on the road.
I ride a particularly dangerous and busy road in Birmingham and would not recommend these lights be used as the sole means of "being seen" but they give an interesting little opmh to your tires and have people turning to watch you go by. I find myself distracted by the lights at times. They only work when the bike is moving which isn't too much of an issue as even the slightly movement sets them flashing. I ride 3 miles every day and they are doing well, I would like to point out my Green lights, look decidedly blue but they have a wicked blue/green contrast when in motion. As previous feedback has stated a tiny little plastic cover has to be removed before the lights work- the packaging does not make this clear.
I would recommend them to anyone wanting something a little funky and different for their bike. I am even tempted to buy a spare set I love mine that much. They screw on easily and take normal watch batteries. I've had mine a while now and they are still going strong on the first set of batteries.