Let the Lumenok help you tune your equipment and your shooting skills. The Lumenok H is made to fit .233" ID carbon arrows. This nock repalces original internal mount nocks, and lights up automatically when seated against carbon or aluminum shaft. Battery retention components allows for the battery to be changed easily for the brightest operation possible. It stays lit for up to 40 hours, and does not require magnets, glue, switches or moving parts. With the Lumenok H in your arrows, you will never fail to see shot placement.