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. 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. Polycarbonate blend Nock with aluminum shaft Bright Green LED Illumination Auto ON when nock is shot LED Stays ON until user unclicks the nock Universal collars fits Arrow Shafts (G/X/H/S) Package of 6