Flex Fletch LIT Lighted Arrow Nocks .204 Green 3 pk. Fits most carbon shafts with an ID of 0.204";External on/off switch, no tools needed;Super bright: visible day and night;Long-lasting: stays lit for up to 48 hours;Auto on: lights up when the arrow is shot;Cost-effective: saves expensive arrows;Weight: 18 grains;Pack of 3 lighted nocks