Dinotte's 4 AA LED light is bright small and robust. I like how it kind of disappears on the bike until you need it. I generally leave mine on all the time so I have it when I need it. I seem to often find myself out after dark when that wasn't part of the plan in the AM when I left for my ride. Since it uses standard rechargeable AA batteries you can buy new ones cheaply and share them amongst your other battery powered devices - much better than a proprietary battery. The velcro and o-ring mounting system is secure yet allows you to move it between bikes in a few seconds.