Feature: About 48 hours of battery life (non-replaceable). Bowstring Activated On-off Switch. Lightweight and precision-balanced for superior accuracy. 0.165 nock with 0.204 collar fits 0.165 and 0.204 ID arrows. Specifications: Color: Green, Red, Blue, Flash Weight: 20 grain How to use: Nocks can be inserted to the shaft easily and in fully operational condition. If need to use the collar, assemble the collar first then the nock. Automatically lighted after shoot, there is no need to turn it on manually. Nocks can be turned on or off by Up switch. Package included:3pcs 4.2mm lighted nocks, 3pcs 0.204 collars Any questions, just feel free to contact us! We'll respond you soon!