Nockturnal's Red Lighted S-Nock features exclusive patented linear switch that is design works every time, no wires or connections. The simple bowstring activated push-on switch easily switches off when done and offers an extended burn time of 20+ hours. This lighted nock is waterproof and weatherproof so you can use in any conditions. See your arrow impacts under any light and find that arrow on pass-through shots. Great for bowfishing! Features: Bowstring activated linear switch. Fool-proof operation in any condition. Long life lithium battery. Super bright LEDs. Waterproof and weatherproof. Unsurpassed reliability. Fits standard carbon .244 ID shafts. Each nock weighs approximately 25 grains. 3 per pack.