The Nockturnal FIT strobing nock redefines arrow visibility and reliability with a robust, universal-fit design and advanced illumination system. Compatible with virtually every arrow on the market, this nock includes adapter sleeves for GT, S and H-diameter shafts and fits X-diameter arrows out of the box. Constructed from durable, impact-resistant clear polycarbonate, each nock houses dual LEDs that strobe 400 times per minute in alternating red/green, red/blue or green/blue patterns. Powered by a long-lasting lithium battery that exceeds 20 hr of continuous strobing, activation is instantaneous thanks to the patented string-activated, piston-driven contact switch. Deactivation is simple using the Nockturnal nock tool or a broadhead tip. At just 25 grain, it offers superior tracking in both daylight and darkness-making shot recovery easier than ever. Constructed from ultra-durable clear polycarbonate, this item offers superior strength and impact resistance Each nock in this set has a precise weight of approximately 25 grain for consistent arrow flight A 20+ hr battery life keeps you running through extended hunts or surveillance sessions Convenient 3-pack ensures you always have a spare when it matters