Almost all bicycle rear lights use LEDs instead of filament bulbs as they are more reliable and use much less battery power, whilst also offering much higher levels of brightness. Used in flashing mode, they are very good at attracting attention from other road users. It's advisable to use at least two rear bike lights, a common configuration is one flashing and one in constant, this is highly advisable just in case one stops or becomes obscured.
In order to cycle on the road it may be a legal requirement in your country to use a light certified to a specific standard or an international equivalent. Most but not all lights sold on Wiggle are certified and labelled with a European CEN standard. Please check your country’s requirements to see if this is sufficient and if necessary contact the manufacturer to see if this light has been additionally certified for your country. Strangely some of the very best lights are not legal on their own and should be used with an additional legal backup light.
For information on the current, often confusing, state of UK law please click here