H2Glo lighted nocks ONLY FIT our Tiger Shark LGT series arrows. They will NOT fit the Fiberglass or Carbon Spined shafts. To use, just pull out the replaceable nock that comes with the arrow and insert one of these nocks. Nock will automatically light up when the arrow is released. Small switch on nock turns it off when not in use to save on battery. Nocks comes in a package of 3 and glow red when lit.