Designed to fit nearly every hunting arrow on the market, the Nockturnal FIT non-strobing base nock will fit X-diameter arrows. Each 3-pack of FIT nocks includes 3 sets of Nock Collar adapter sleeves to fit GT, S and H arrows. Each FIT nock features ultra-strong, impact resistant, clear polycarbonate construction to encapsulate the super-bright single LED that is activated by a patented string-activated, piston-driven linear contact switch. Like all Nockturnal nocks, the FIT reliably activates immediately when the string is released, and it can be switched off quickly and easily with the Nockturnal Nock Tool, a small screwdriver or most broadhead tips via an opening in the side of the nock. With well in excess of 20 hours of lithium battery life, each Nockturnal FIT weights approximately 25 grains and will remain brightly lit for plenty of time of arrow retrieval and can be easily spotted in daylight or darkness. Features: Super strong clear polycarbonate construction. Fits X, H, S, and GT Arrows. H (white bushing) = Fits smaller diameter carbon .233 ID shafts. GT (black bushing) = Fits smaller diameter carbon .246 ID shafts. S (gray bushing) = Fits standard carbon .244 ID shafts. X (no bushing) = Fits smaller diameter carbon .204 ID shafts. Weighs approximately 25 grains. 20+ hour battery life. 3-Pack.