NAP 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 green or red and are offered in a 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.