Flex Fletch LIT Lighted Arrow Nocks .166 Set of 3 Green. 166". Each nock features an external on/off switch for easy activation without tools and automatically lights up when the arrow is shot making it visible both day and night. With a long-lasting battery that stays lit for up to 48 hours these nocks come in a variety of colors including red blue green yellow or multi-color and are a cost-effective way to preserve expensive arrows. Each pack contains three lighted nocks weighing 16 grains each. Features of Flex Fletch LIT Lighted Arrow Nocks: Fits most carbon shafts with an ID of 0.166" 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: 16 grains Pack of 3 lighted nocks Package Contents: Flex Fletch LIT Lighted Arrow Nocks Flex Fletch LIT166GR12: LIT Lighted Arrow Nocks .166 Set of 3 Green