I haven't had much time to play with the sirens, but the flag sometimes has trouble pulling the pin, I have been adjusting the length of line to the flag and find that the more line you give it, the more momentum the flag gets, but it still doesnt always trip.
But watch out, these things are LOUD. Sounds like a car alarm. I doubt I will use the siren portion much, but you can set it to only flash lights.
They seem very well built.