Last year I bought 4 packs of nocturnals for 4mm arrows. In 12 nocks, only 2 worked and most switches broke. I was able to return them and at this point will never go back to the nockturnals. I ended up buying the cheap ones off amazon and they all worked, plus they were about 80% cheaper. This year, I am not doing lighted nocks. I think they are a great aid after the shot, but its not worth messing around with, at least for me. I have reflective wraps on my arrows that I've come to prefer over light nocks. Plus I hate practicing with them. I don't like to see where I hit until I get to the target. The bag targets at the range sometimes allow an arrow to droop, which can skew my perception of where an arrow hit, and that messes with my mind when I'm shooting.