This is the battery-powered version of the excellent dynamo-powered Toplight taillights from B&M. Two AA batteries are included. The mounting bolts are 50mm apart so it will work with any of the Tubus racks we sell and many others.
The light from two LEDs is spread into a broad line across the width of the light, providing increased surface area and making it more visible at a distance. Side visibility is also very good.
The Toplight is controlled by a three postion switch - on/off/Senso. The Senso position enables the light and motion sensors in the taillight. When the bike is moving and it's dark, the light is automatically switched "On". When you stop, the light stays on for a few minutes before switching off. It stays off until the bike resumes motion. Pretty slick!