Nocturnal Lighted Nocks Helios H Nock/Fletching Combination (3-Pack) High-performance breakthrough design - the new Aero foil vane design increases spin and is virtually unaffected by crosswind. Featuring the same high visibility and Pinpoint accuracy from Nockturnal High visibility - with long lasting lithium batteries, you can shoot it at dusk, and with 20+ hours of battery life, you can still find your arrow the next day No assembly required - nocks can go straight from the package to the shaft in Fully operational condition. Just insert it, and you are ready to shoot Helios H - fits Easton St epic and St excel Nockturnal - leading the revolution in lighted nocks