Jreameast 3pcs High-visibility 6.3mm 0.248" Blue GT Size LED Lighted Nocks Bowstring Activated On-off Switch About 30 hours of battery life(non-replaceable) Fits arrow shafts with Inside Diameter of 6.3mm(0.248") Bowstring Activated On-off Switch Waterproof and shock resistant.No assembly required Fits most standard arrows.