Manufacturer Part Number (MPN) : NT-732Nockturnal Predator Crossbow Nock Size 2 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. The reliable piston driven contact switch ensures L.E.D. illumination every time. Waterproof and shock resistant design is second to none. Long lasting lithium batteries allow you to shoot it at dusk, and with 20+ hours of battery life, you can still find your arrow the next day.