Powered by Lumenok, RED HOT Lighted Capture Nocks by Parker Bows are engineered for modern, high-performance crossbows. The exclusive, patented design is made for safety and accuracy so you know exactly where your arrow is. The nock lights up when the arrow is shot. Easily switch off the light by pressing on the nock. Battery life of over 40 hours and utilizes a standard replaceable battyer (BR 425). Mass weight: 28 grains each. Comes in a pack with three nocks. RED HOT Lighted Capture Nocks fit the following crossbow arrow brands: Parker Hunter Arrows (2013 and up), RED HOT arrows (2014 and up), and others with inside diameters of 0.300". Note: Will not fit Carbon Express RED HOT arrows.