Nockturnal 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. 20+ hours of battery life No prep work needed Waterproof and shock resistant Piston driven contact switch Red LED illumination every time Size 2 for Horton, Gold Tip, and several others including Easton Works in place of half moon, Flat, or Capture nocks