The Tidy Seed No-Mess SMALL Bird Feeder is designed for pet birds up to the size of a Cockatiel. The Tidy Seed small measures approximately 5" x 5" x 4.5" (OTHER SIZES ARE AVAILABLE FOR LARGER BIRDS) The clear Acrylic design keeps the feeder from becoming cloudy over time like plastic will. Also, the acrylic perch is much more sanitary than the wooden competitors on the market since this feeder can be hand washed whenever needed. The feeder comes with (2) sets of pre-drilled holes and 2 screw hooks for you to pick the set of holes you wish. Tidy Seed can be hung inside or outside the cage depending on which set of holes you choose. (PLEASE DO NOT OVER-TIGHTEN THE HOOKS AS THEY WILL BREAK OFF IN THE FEEDER) To fill Tidy Seed, simply turn it face up and pour in the seed then rehang in or on cage. To empty Tidy Seed, remove from cage and turn it face down over the garbage or seed sorter. The obvious benefit to the Tidy Seed No-Mess Bird Feeder is the significant reduction in seeds/hulls on your floor and valuable time savings. The hidden benefit is the savings in your seed costs. Instead of your bird sifting through the new food for their favorite and spilling out most of the rest into the bottom of the cage where it is lost, they still sort through it but the rest is contained in the feeding area for your bird to come back to later. You may find the need to use a small bungee strap if you hang Tidy Seed on the outside of your cage, especially if you have more than one bird in the cage. Sometimes one bird will hold the feeder out while the other(s) escape, so be careful if this fits your circumstance.