The Nite Rider Solas 250 uses two powerful LEDs to produce an amazing 250 lumens of light output. It features 4 modes (2 flash / 2 steady) & is USB (Universal Serial Bus) rechargeable. It also featuresl Group Ride Mode for cyclists who want to stay visible but not distract others in the pack. Daylight Visible Flash (DVF) 250 lumen super bright tail light Group Ride Mode be seen without distracting fellow cyclists Easy on & off seat post strap mount with quick release tab Convenient USB (Universal Serial Bus) rechargeable Super bright daytime flash mode Be Seen by cars = Be Safe FL1 Standard IP64, dust & water-resistant Lumen Output:250 Run Time:4:30 40:00hrs Charge Time:4:00hrs Weight:82g Battery: Li-Po