Flex Fletch LIT Lighted Crossbow Nocks. Each nock features an external on/off switch for easy activation without tools and automatically lights up when the arrow is shot making it visible both day and night. With a long-lasting battery that stays lit for up to 48 hours these nocks come in a variety of colors and are a cost-effective way to preserve expensive arrows. Each pack contains three lighted nocks weighing 16 grains each. Specifications for Flex Fletch LIT Lighted Crossbow Nocks: Manufacturer: Flex Fletch Color: Green Features of Flex Fletch LIT Lighted Crossbow Nocks: .300 diameter External on/off switch Automatically activates on launch Visible in daylight and nighttime conditions Battery life up to 48 hours Weight: 16 grains each Includes 3 lighted nocks Package Contents: Flex Fletch LIT Lighted Crossbow Nocks