Jreameast 3pcs High-visibility 6.2mm 0.244" Red S Size LED Lighted Nocks Bowstring Activated On-off Switch About 30 hours of battery life(non-replaceable) Fits arrow shafts with Inside Diameter of 6.2mm(0.244") Bowstring Activated On-off Switch Waterproof and shock resistant.No assembly required Fits most standard arrows.