Safrone 5 Packs of Archery S Light Arrow Nock LED Lighted Nocks Red for 6.2mm shaft Lightweight and precision-balanced for superior accuracy Indexed nock end provides added safety and easy ON/OFF design Fits any bolt with inside diameter 6.2MM Package includes 5 pieces lighted nocks Note: it's not activated by the force of launch.before firing your arrow,please put the battery pin into the nocks,it will turn on.On the contrary,it will light off.