Nockturnal Nockturnal-X Lighted Nocks 20+ hours of battery life - you can still find your arrow the next day Fits arrows with inside diameter of .204 No assembly required.Piston driven contact switch ensures L.E.D. illumination every time Waterproof and shock resistant design is second to none Plastic package,come with a small screwdriver which can help you turn off the nocks easy.