The Niterider Sentinel 250 Rear Light is designed to increase cycling safety by way of 2 varying flash patterns and 2 steady beams (high/group ride mode). Behind the durable red lens and casing are two powerful leds that emit 250 lumens in the brightest daylight visible flash setting, allowing you to be seen day or night. For enhanced safety, the laser lane modes (3) are designed to project ultra-bright laser lines on the ground. This creates a virtual lane for the rider, further increasing visibility.  Niterider Sentinel 250 Rear Light Features Daylight visible flash (dvf) Highly visible laser lanes All in one, laser and tail light! Convenient usb rechargeable Group ride mode – be seen without distracting fellow cyclists Easy on and off seat post strap mount with quick release tab Fl1 standard ip64, dust and water-resistant