Bullet Points: 1HIGH VISIBILITY and LONG LASTING LITHIUM BATTERIES - Shoot it at dusk, and with 20+ hours of battery life, you can still find your arrow the next day 2RELIABLE - Piston driven contact switch ensures L.E.D. illumination every time. Waterproof and shock resistant design is second to none 3NO ASSEMBLY REQUIRED - Nocks 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 4FITS ARROWS WITH INSIDE DIAMETER .244 5Piston driven contact switch ensures L.E.D. illumination every time Features: This product is the latest,More convenient When you use other product ,the batteries maybe Loose,but this product will not Diameter: For 6.2mm Shaft Fits any bolt with diameter 6.2MM. Don't need light it in advance before shoot Easy and durable usage, more competitive price The nock will be automatically lighted after shoot After arrow retrieval simply push back activator switch located in side of nock to the off Battery ( non-replaceable ) last about 24-48 hours Note: This is not a toy, do Not shoot at people Specification: Nocks diameter:6.2mm Quantity:12pcs Color: red What is included: 12X Arrow Nock