Size: 1 - Suitable for finches and birds of similar size Size: 2 - Suitable for average-sized budgerigars (budgies), parrotlets and small to average-sized lovebirds Size: 3 - Suitable for large budgerigars (budgies) larger lovebirds (often female Peach-face), Bourke’s Parakeets, SMALL Cockatiels Size: 4 - Suitable for most cockatiels, and birds of similar size Size: 5 - Suitable for most SMALL conures (such as Green-cheeks, maroon-bellied, LARGE Cockatiels, etc.), Size: 6 - Suitable for most larger conures (most Sun Conures, Nandays, Jendays, Blue Crowns etc.); Quaker Parrots, Caiques, Regents Parrots , Indian Ringnecks, Port Lincolns, Rainbow Lories, Rosellas, Noble Macaws and birds of that size Size: 7: Fits largest Conures, such as mosts Mitred Conures, Patagonians (lesser & greater), Golden Conures / Queen of Bavaria’s; Red-crowned Amazons. Fits most yellow-collared macaws and the smallest cockatoos (weighing less than 280 grams). Size: 8 - Fts small African Greys (Timneh, etcs.), Galah / Rose-breasted Cockatoos, Gang Gang Cockatoos, Lesser Sulphur-crested Cockatoos, average to larger Goffin’s Cockatoos, Lilac-crowned Amazons, Severe Macaws, Spix’s Macaws, Illiger Macaws Size: 9 – Fits most Congo African Greys, Eclectus Parrots; small Blue-fronted Amazon Parrots, Cuban Amazons, Double-yellow-headed Amazons, larger cockatoos & birds of similar size Size: 10 – Fits most larger Macaws (average Blue & Gold, etc.); large Cockatoos (Greater Sulphur-crested Cockatoos, Moluccans, Palm Cockatoos, Umbrella Cockatoos), larger Amazons (Mealy, Tres-Marias Amazons) and like-sized birds Size: 11 – Fits most Hyacinth Macaws / Large Greenwing Macaws, etc. and like-sized birds Size: 12: For the largest of all macaws – large Hyacinths, and birds of that size.