The Lumenok GT is activated upon the shot to allow archers to follow the path of their arrow. This model Lumenok provides up to 40 Hours of Illumination and can be seen from great distances. No magnets required for activation. This Lumenok is made using a Signature Nock from Bohning. Features: Replaceable Battery - The patented Polymeric battery holder allows for battery replacement and protection against failure due to hard impacts! The Lumenok is a lighted arrow nock used for shot placement recognition & arrow retrieval. Lumenok Signature (GT1) lighted arrow nock fits .246" ID carbon and aluminum shafts. Each Lumenok is equipped with a replaceable battery (Lumenok part # RB).