I have a set of Blackburn Fleas on my helmet. Super bright(not just for their size),almost weightless,and easy to mount. Only complaint is the front runs down quick(about 4-4.5hrs);if it only had 3 LED's it would still be plenty bright,but the batt would last longer.
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C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes,Giant Defy 1,Schwinn DBX SuperSport,Brompton S6L/S2E-X/M6L-X/S12 T Line