Squirrels are innovative rascals. While this bird feeder is not a 100% squirrel-proof, I like mine so well that I'm purchasing one for a house-warming gift.
Love this feeder as do the family of cardinals that bring us hours of enjoyment. It didn't take the squirrels very long to figure out how to outfox it. They hang upside down with their hindfeet an fill their faces with the sunflower seeds.