Squirrel Buster Plus Bird Feeder with Removable Cardinal Ring This posigrip ring system has been specifically designed to attract cardinals. These perennial favorites have two very distinct features: small necks and big feet. They prefer gripping a thick textured perch and facing their food source directly. Cardinals dislike turning their heads to feed. The Squirrel Buster Plus Cardinal Ring perch system allows them to eat facing the seed while providing a secure and comfortable perch. These cardinal friendly feeding features combined with a bush level location make Squirrel Buster Plus very inviting to cardinals. Thick, adjustable-length perches with textured surfaces provide a secure and comfortable grip for small birds. The seed ports will close automatically when a squirrel climbs onto the feeder. Birdwatch America's Best New Product Award. Seed capacity: 3 quarts. Squirrel Buster Plus is also easily assembled and dishwasher safe.