Squirrel proof Holds 3 quarts of seed Weight adjustable to help control unwanted birds Cardinal friendly Dishwasher safe Chew proof Lifetime hassle-free warranty Squirrel Buster Plus breaks new ground with design features available for the first time on any bird feeder. Over a million happy clients (and well-fed birds) confirm that the patented Squirrel Buster system is truly squirrel proof! Openings in the bottom section of the feeder (shroud) align with seed ports, providing birds access to the seed. When a squirrel climbs onto the feeder, its weight automatically forces the shroud down, closing the seed ports. Squirrels and large birds are foiled but not harmed in way.