Clean-Shot Archery Nock Out Crossbow Flat Nock (Pack of 3) UNIVERSAL FIT:Perfect gift for the XBow archers! Dont worry about buying the right size of lighted nocks - there is only ONE package. We include precision bushings to fit the 3 most common carbon bolts - .285", .297" and .300" ID bolts. Practice Mode: The only lighted nock that can be turned off! A simple turn of the silver activation collar deactivates the LED for traveling, 3D tournaments or lightless practice - preserves battery. EASY OFF: The easiest lighted nock to turn off! With the arrow bolt still in the target, simply pull the nock straight back until you hear a soft "click" and the LED turns off - no tools are required. WEIGHT: Approximately 31-34 Grains (depends on bushing size); BATTERY: 24 hours (continuous on time). Battery is disposable. USAGE: Designed for crossbows that shoot up to 350 feet per second (fps). The Nock Out Contender 300 is recommended for high speed crossbows, above 350 fps.