Flex Fletch LIT Lighted Arrow Nocks .246 Green 3 pk. Fits most carbon shafts with an ID of 0.246" (6.2mm);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: 25 grains;Pack of 3 lighted nocks