This is a spare rear light/tail light for long-distance rides, brevets, or even as a light for camping rides. It can flash or stay lit. It lasts approximately 15 hours when flashing and about 8 hours when lit. It's quite bright. It will be shipped with button batteries installed. Please note that the included batteries may not last the full duration. It runs on two button batteries. It's better suited as a backup light rather than for everyday use. It uses CR2032 batteries, which are readily available at convenience stores even in the middle of a brevet. Road bike Cross bike Mountain bike Cycling Bicycle Light Rear light Tail light Brevet Spare Long distance Camping Ride