I have RO'ed for PRS matches with these indicators on the target. One stage had one target, 10 rounds per shooter under 500 yards. Indicated every hit for the day with over 100 shooters.
The clear part that sticks out is like a gel, we watched one bullet pass through it. The indicator will still function with multiple holes in the gel. The light is behind the steel, and is directed up into the gel, so it stays functional. I have seen ones with about a dozen holes in it, still works well enough to see through a spotter at 1100 yards. They will also be selling the replacement gel parts for fairly cheap if you happen to shoot yours up.
We had the indicator set to mark impacts only, and didn't have any problems with it.
I will be buying one for my own shooting.