Jreameast 3pcs High-visibility 5.3mm 0.209" Blue X Size LED Lighted Nocks Bowstring Activated On-off Switch About 30 hours of battery life(non-replaceable) Fits arrow shafts with Inside Diameter of 5.3mm(0.209") Bowstring Activated On-off Switch Waterproof and shock resistant.No assembly required Fits most standard arrows.