Firenock lighted nock system is not just an ordinary lighted nock, it can be customized in the way you want. You can select model of battery to match your requirement; BL for low to high temperature environment (-4 to 180 F) while BR for extreme low temperature environment (-17 F). You can change your lighted nock system from hunting to intermittent to hunt for turkey and ground blind shooting. You can change your nock color from red to blue / green if you are hunting only during night time to enhance your hunting experience. You can buy O-rings, nocks, end caps and matched weights in case you need them. Furthermore, you can make your Firenock lighted nock system to function even under 20 m deep in saltwater for weeks using Hydro Bow Fishing System. Please click below to see all Firenock lighted nock system accessories. Enjoy!