10 watt Single beam system with 4.0Ah NiMH battery. The new NiteRider Evolution system features a 4.0Ah NiMH battery pack which can be placed in a jersey pocket, hydration pack or strapped to your bike. The battery pack is small enough to fit on almost any frame. This system comes with both a handlebar and a helmet mount. Switch as the situation demands. Features: New 4.0Ah Nickel-Metal Hydride Rechargeable Battery, New Multi use battery pack can be mounted on bike for handlebar use or placed in jersey pocket or in a hydration pack for helmet use, New SurLok Connectors, Frame mountable battery using included strap, Multi-position helmet and CamLok™ QR mounts, 10w Hi-Efficiency Halogen Bulb Overnight 9 hour charger, System weighs 20oz (Mount, Light head & Battery. Burn Time: 2:20hr @ 10w