The Squirrel Buster Mini is guaranteed to be squirrel proof. Openings in the bottom of the metal mesh shroud are aligned with the seed tray and allow birds access to the seed. When a squirrel climbs onto the feeder, its weight automatically forces the shroud down, closing access to the seed tray. Squirrels are shut out but not harmed in any way. The negative grip tube is part of our patented technology. It prevents squirrels from grabbing the wire hanger with their hind legs, hanging down alongside the feeder, and defeating the closing mechanism. Both perching and clinging birds love this feeder. The seed ports have perches for the perching birds but the metal mesh shroud also offers a large clinging area. Because of the combined perching and clinging surfaces, you will find an enhanced level of bird activity with the Squirrel Buster Mini. The feeder also features a patented Seed Tube Ventilation System to keep birds healthy. Transparent seed tubes are like greenhouses, they trap solar energy. Traditional seed tube cover designs block the escape of heated air. The patented Seed Tube Ventilation System in Squirrel Buster Mini permits humidity and hot air to escape through vents at the top of the feeder. The escaping hot air is replaced with fresh air entering the seed ports and openings on the bottom of the seed tube. The seed stays fresher and attracts more birds.