Jeff,
I have had a couple not light up when they were shot. But for the most part they work great. I just fixed the problem by making my own and having the light on all the time.I have also shot deer with them that the nock was lit when it went into the deer but not after it went thru the deer. I guess something in the pass thru pulled the nock out enough to turn the light off. You can get the thill lite in green also. Use that with a green nock and it's like a flsh light..LOL Much briter then the red nocks. But I wouldn't use the green in the ones I leave on all the time. They are to brite when it starts to get dark.

MC