The Squirrel Buster® series of feeders uses a Truly Squirrel-Proof™ design with an adjustable spring closing mechanism that controls how much weight the metal mesh shroud will support. Birds can land on the perches and feed freely, but when a squirrel climbs onto the feeder, it's weight automatically forces the shroud down closing access to all seed ports. The largest-capacity model, the Squirrel Buster® Plus squirrel-proof bird feeder is also our most popular. Measuring 28" tall from base to hanger, the Squirrel-Buster Plus holds a whopping 5.1 lbs of birdseed and features our patented Cardinal Ring System™. Fully weight adjustable, you can fine-tune your feeder to exclude larger birds.