The mounting holes are 50mm apart, just like most other Busch & Müller taillights. The single LED glows bright red, so don't be fooled by the clear lens. And the optics in the lens spreads the red light across the width of the lens, so the driver behind you sees a lot more than just a point source of light. This has a standlight, so it will stay lit for several minutes after you stop.
For dynamo powered generator light systems.