Proven Technology squirrel Buster PlusTM breaks new ground with design features available for the first time on any bird feeder. Thousands of delighted clients (and well-fed birds!) confirm that the patented squirrel Buster TM system is TRULY sQUIRREL PROOF. Guaranteed squirrel and Large Bird Proof Effective against Red and Gray squirrels, as well as Grackles, starlings, Doves, etc. Dishwasher safe Design Easily cleans to maintain a safe and healthy feeder Built-to-Last Construction UV-stabilized ABs and polycarbonate resins, rust-proof / powder-coated aluminum and stainless steel components. How it works 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 any way. All squirrel BusterTM products are made of rugged UV-filtered ABs and Polycarbonate resins and powder-coated aluminum components. Hangers, springs and fasteners are stainless steel