Axe Crossbows Red Lit Nocks - The metal injection molded Lit lighted nock system creates an audible click when properly secured to the crossbow's string. The super-bright LED system is initiated by the forward movement created by the strings forward movement to engage Nockturnal's patented crossbow string-activated linear switch with piston-driven assembly. These lighted nocks are exceptionally reliable and do not require any specific tools to set up and come factory-installed in the shafts. Side illumination ports on the nock's body allow for additional light dispersion and increased "tracking" as the nock moves. With more than 20 hours of lithium-powered battery life the extended burn time grants plenty of opportunity for reuse and easy identification long after the shot. Designed To Fit AX405 .166 Diameter Crossbolts Crossbow String Activated Injection Molded Super Bright LED 20+ Hours