Nockturnal’s Strobing FIT Nocks offer outstanding reliability in the worst possible conditions. They provide a vital indication of where your arrow hit the animal, and also aid in locating your arrow if you miss. The FIT Nocks utilize a piston-driven, bowstring activated linear contact switch to keep operation simple and intuitive, and are both water and weather proof. Deactivating the FIT Nock can be performed with the Nockturnal Nock tool, a small screwdriver, or a common broadhead tip via an opening on the side of the nock. Each FIT Nock feature an ultra-durable, impact-resistant clear polycarbonate construction that protects the super bright LED, and includes three sets of Nock Collar adapter sleeves to fit GT, S and H arrows. Features: Super Strong Clear Polycarbonate ConstructionAvailable Colors: Red/Green, Blue/Green, Red/Blue, Red, Green, Blue, Orange, White, PinkFits X, H, S, and GT ArrowsH (white bushing) = Fits smaller diameter carbon .233 ID shaftsGT (black bushing) = Fits smaller diameter carbon .246 ID shaftsS (gray bushing) = Fits standard carbon .244 ID shaftsX (no bushing) = Fits smaller diameter carbon .204 ID shaftsEach nock in this package weighs approximately 25 grains20+ Hour Battery Life3-Pack Nockturnal FIT Universal Strobing Red & Blue Lighted Nock 3pk NT-310