Activated by the force applied to it at the firing of the bolt. The shooter is able to follow the path of is arrow to his target. In the case of an errant shot, the lighted nock will make finding your arrow much easier, saving time and the cost of the arrow. The Lumenock is visible for great distances in the dark. It can remain lit for 40 hours, allowing an archer to return hours after a shot to retrieve an arrow. Recommended for Excalibur Firebolt and .302" inside diameter carbon bolts.