Tail lights are installed in the back of a bike to show other road users the presence of the bike and to indicate that the bike is slowing or stopping when the brakes are engaged. During hours of limited visibility, especially in dark conditions, the bike tail light needs to emit a red light capable of being seen and distinguished from a distance of 500 feet to the rear. As a crucial safety factor, a bike tail light utilizes LED technology to create eye catching visibility in both day and night. It is typically built using an array of SMD LEDs that deliver up to hundreds of lumens. An ultra-wide angle red lens distributes light for long-range visibility when viewed directly from the rear but additionally provides ample surrounding light to the peripheral for maximized side visibility. Tail lights designate the rear of a bicycle by a steady burning light. Some products are equipped with sensors that can detect vibration, motion and even changes in the level of light radiated from the rear. Upon detection of a sudden stop motion or other sources of light, the lights will increase the light output or switch to a flashing mode to compete for the attention of other road users. The LEDs are powered by an on-board battery. LED tail lights must be durable, weatherproof, impact and vibration resistant so they can stand up in tough operating environments.