KNOG Pop Duo Light LEDS- 1x Super-bright SMT LED designed to provide maximum brightness for duration of run time, Rear LED generates 5 lumens for 3/4 mile+ visibility SIDE ILLUMINATION- Giving riders 180 visibility BIKE ATTACHMENT- Tool-less attachment for seatposts 22-32mm diameter. Can change orientation of rear light by rotating 90 LOW BATTERY INDICATOR- A red LED will shine from the front of the light when the batteries are low. This LED will remain on for 5 seconds after the light is switched off to indicate that batteries need changing. BUTTON- Longer button push on (0.75sec) prevents accidental turn on. Short presses switch modes continuously.