I'm shooting the Luminock and the Firenocks. Lumis is my Phoenix and Vortex. Work great but the battery is not replaceable. No magnets, prepping the back of the carbon arrow (sanding lightly0 is essential to good operation. Firenocks, in my Cyclone. Expensive. WQork great, can change battery. Both add about 15g to back of arrow over usual nock. FWIW, only use them for low light conditions.
Cost of arrow with Firenocks (+$30)! Becomes questionable if worth it, since even a lighted arrow - buried in woods litter- won't be found.