This morning I got up early and let the dogs out only to hear a racket from the AC unit. When I checked a large Cuban tree frog had managed to get hung up in the fan and was being beat by the blades. It was too late to save it, but I still have to wonder how it got there in the first place. Those things can get into anything, especially your vents and from there your toilets. Critter Quitters stop this while protecting your vents from damage. So if you use lead to seal, or even if you dont, Critter Quitters are a good option, and you may save a frog or so.