Tthese little gems are O.K. and do work well to keep bees of most kinds out of the nectar; however, there is just no humane way to rid one's yard of bees.  Even though bees are a pain and create a problem for some hummingbirds these guards manage to keep the bees at bay.  Our hummers just look at the bees gathered around the guards and laugh at them while eating the nectar.  Typical of most predators the bees attempt to chase the birds but success falls to the birds.