Powered by Lumenok the Lighted Capture Nocks feature a patented design for safety and accuracy. Engineered for modern, high performance crossbows. Light when the bolt is shot, turn off by pressing the nock. 40 hour battery life, uses replaceable BR 425 batteries. Weigh 28 grains each. Fits RED HOT (2014) Parker Hunter Arrows (2013 and 2014) and other bolts with a .300 inside diameter. 3-pack. Red.