The Nockturnal Launchpad Crossbow Nock is easy to install, easy to use, and specifically engineered to light up every shot with high-visibility LEDs. The lightweight, durable design is fully adjustable and can provide a custom precision fit on virtually any brand of crossbow bolts. Product Features Durable & Long-Lasting Integrated, one-piece aluminum housing protects battery and LED during high-speed flight and impact. Custom-Fit Micro-Adjustability, adjustable barrel end is easy to install and provides a reliable performance fit. One Size Fits nearly all crossbolt brands and models (comes with 2nd Grey Collet). Includes reusable c-clip to prevent lighting during storage. Easy & Reliable On/Off Indexed nock end provides added safety and an easy ON/OFF design. Each nock in this package weighs approximately 30 grains 3 per package