Nockturnal Predator Crossbow Lighted Arrow Nocks - 3 Pack HIGH VISIBILITY and LONG LASTING LITHIUM BATTERIES - Shoot it at dusk, and with 20+ hours of battery life, you can still find your arrow the next day RELIABLE - Piston driven contact switch ensures L.E.D. illumination every time. Waterproof and shock resistant design is second to none NO ASSEMBLY REQUIRED - Nocks can go straight form the package to the shaft in fully operational condition. No prep work needed. Just insert it, and you are ready to shoot SIZE 1 FOR SMALLER ID BOLTS - Designed to function as Half Moon, Capture, and Flat with 1 Universal Design RED 3 PACK - Also available in Green