Polycarbonate blend Nock with aluminum shaftBright LED IlluminationAuto ON when nock is shotLED Stays ON until user unclicks the nockUniversal collars fits Arrow Shafts (G/X/H/S)Available in packs of 3 or 6NAP Thunderglo Lighted Nocks have ultra bright LED illumination and feature an easy on/off feature. Thunderglo Lighted Nocks are crafted of a polycarbonate blend with an aluminum shaft making them extremely durable for long lasting use and life expectancy. Thunderglo Nocks comes in blue, green or red and are offered in a 3 or 6 pack. Universal collars will allow Thunderglo Nocks to fit most any arrow (G/X/H/S). For the ultimate in lighted nocks, trust the NAP Thunderglo.