This is a spare rear light/tail light for long-distance rides, brevets, or even as a light for camping rides. It has both flashing and solid modes. Flashing mode lasts approximately 15 hours, and solid mode lasts approximately 8 hours. It's quite bright. It will be shipped with button batteries installed. Please note that the included batteries may not provide the full stated run times. It runs on two button batteries. It's better suited as a backup light rather than for everyday use. Since it uses CR2032 batteries, you can easily find replacements at convenience stores during a brevet, even at night. Road bike Cross bike Mountain bike Cycling Bicycle Light Rear light Tail light Brevet Spare Long distance Camping Ride