Usage Tips:[Compatibilities]Keuaaao X lighted nocks fit arrows with .204 Inside Diameter, bushings matching and easy installation [Brightness]These nocks emit a vibrant and highly visible light, making it easier to track your arrows, the winter holiday season, visible in darker evenings, help watching trajectory, enhancing accuracy and retrieval [/Off]The light automatically when fired, and slider switch to shut off, bowstring activated linear switch so easy [Battery Life]Great battery life of LED lighted nocks: Up to 48 hours, the light is very bright even in midday sunlight [Practicality]These lighted nocks for arrows are excellent for archery hunting target in the winter, in darker evenings, in bright daylight, even 3d tournament, help watching trajectory and find the . They are a fantastic addition for any archer seeking enhanced shot visibility! Colour: Red Material: Plastic Package Contents: 12PCS x Lighted Nocks for Arrows Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.