With no-fail internal components and bowstring activated dependability, Halo Nock provides superior, dependable performance with every shot. Sold in a 3 Pack Halo Nock provides superior, dependable performance with every shot. Their patent pending design wont accidentally turn on when placing on your bowstring. No matter how hard you push on the nock, it won t activate until it leaves the string. In addition, this innovative design avoids any risk of a mini-dry fire that can occur with other lighted nocks that slip forward during release. Product Features FIT- A multi-fit package with bushing adapters to fit most common arrow IDs of .204 , .233 , and .244 -.246