I was one of the first to give rave reviews to 4sevens 100db titanium whistle. Tonight I blew on it—and nothing. I carry it on a key carabiner attached to a belt loop. During the last several weeks of carrying this way, the white nylon insert had moved down so that it was flush with the mouthpiece. I would have eventually lost it had I not noticed. I pushed it back into position so that it was flush with the notch, and then used a tiny dab of JB Weld on each side to hold it into place. I think this will solve the problem, but I will definitely be keeping an eye on it. If you own one, you might want to do the same.