Sifter-Style Bird Feederis a durable hopper-style feeder that Eliminates Unappetizing Feed Fines and Dust; it has a Full Screen Back that sifts out fines yet Prevents Pellets from Falling Through. Our Bunny Wonder Solid-Style Bird Feederis a durable hopper-style feeder that is recommended to Use When There is Little or No Problem of Fines or Dust.