The Nockturnal Launchpad Universal Crossbow Nock is easy to install, easy to use, and specifically engineered to light up every shot with high-visibiLightedy LEDs. The lightweight, durable design is fully adjustable and can provide a custom precision fit on crossbows requiring a half-moon nock. Features: Integrated one-piece aluminum housing protects battery and LED during high-speed flight and impact. Adjustable barrel end is easy to install and provides a reliable performance fit. One size fits nearly all crossbolt brands and models. Reusable C-clip to prevent lighting during storage. Easy and reliable on/off indexed nock end provides added safety and an easy on/off design. 3 nocks per package; Each nock weighs approximately 30 grains.