The Lumenok comes on when shot from your bow and stays on until you turn it off. The Lumenoks 3 volt lithium battery has a 5 year shelf life and will stay lit continuously for 40 hours. They work great for hunting and target shooting. The Lumenok aids the archer with bow tuning .You can see erratic arrow flight much better because of the light on the end of the arrow. Practicing at greater distances allows the archer to immediately associate the result of a shot with his effort. The archer’s ability to see the arrow from release to impact at distances beyond 100 yards allows unprecedented rapid feedback to the shooter, even with today’s fastest bows. If your bow needs tuning, or your form needs improvement, the Lumenok will help you realize it and address those issues. Lumenok is the simplest to use lighted arrow nock on the market, we guarantee it! Get yourself some Lumenoks today online or ask your local dealer about them