3PCS Shooting Automatically Lighted Nock Compound Bow Led Lighted Arrow Nock This product is the latest Arrow Nock,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. 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