Purchased these replacement yellow bee guards (which differ in shape from the image on the Amazon site  the guards now have a semi-globe shape), because I have the careless habit to walk out of the house and walk across the lawn, with a newly cleaned and filled hummingbird feeder held upside down.  On occasion, after a forgetful moment, I re-install the freshly cleaned bee guards before I reach the hummingbird location.  Once in a while, the bee guards have dropped out (and customarily I located them again.)  The last time I didnt.  Long story, irrelevant to the product review, I just realize.  Be it as it may, I have no issues with the bee guards, nor (more importantly) do the hummingbirds.  This past season, the guards functioned flawlessly, to the delight of our hummingbird population (and frustration of the yellow-jackets.)  The only time (no joke) the bee guards didn't make it, was when a black bear roamed the property and totally demolished all of our hummingbird feeders (no joke )  I don't expect Perky-Pet to take that into consideration (sarcasm.)