The Blackburn 2'Fer light set are clever little lights that allows you to choose whether or not you would like to run it as a tail light (20 lumens) or head light (60 lumens).  Waterproof and USB rechargeable the 2'Fer attaches just about anywhere.  Versatile beyond just a front/rear set- need extra illumination on the front of your bike- run both of them, or put one on your backpack and seatpost for extra rear visibility. SPECS Weight  18 grams BATTERIES 1 LITHIUM POLYMER BATTERY INCLUDED (1.1 LITHIUM BATTERY ENERGY CONTENT WATT HOURS) IP STANDARD WATERPROOF TO IP-65 STANDARD MICRO-USB RECHARGEABLE CHARGES VIA ANY STANDARD USB PORT (CHARGING CABLE INCLUDED) RECHARGING TIME 3-HOUR RECHARGE LUMEN OUTPUT / RUNTIME Front/Solid 60 lumen, 1.5 hr runtime; Front/Flash 60 lumen, 5 hr runtime; Rear/Solid 20 lumen, 1.5 hr runtime; Rear/Flash 20 lumen, 5 hr runtime