Advancing the lighted nock design by which all others are judged, Nockturnal Shift G Series of lighted nocks take the simplicity and reliability of the world's most dependable and user-friendly lighted nock to an entirely new level. Thanks to the external on/off switch the process of turning an ultra-bright, string-activated Nockturnal lighted nock-off has never been easier. Just slide the switch and the nock turns off. It's that simple! With 20+ hours of long-lasting battery life and a durable design, these nocks are built to last and perform like none other. Constructed of an ultra-strong, impact-resistant, polycarbonate casing that protects the super-bright LED lights Shift nocks deliver on what users have come to expect from Nockturnal lighted nocks. The patented, string-activated, piston-driven contact linear switch triggers the nock to illuminate immediately when the string is released and can be quickly turned off with the external switch, a true evolution in the world's most reliable lighted nock system. The G Shift is sized specifically for .166 ID arrows and offers increased strength and durability from previous models. Bowstring activated linear switch Super Strong Clear Polycarbonate Construction Streamlined tool-free on/off switch 3 Pack with Universal FIT Collars Available in Red, Green and Red/Green Strobe Fits G Sized Arrows (.166a ^2) 20+ Hour Battery Life