The size of the birds leg ring (inner diameter)
2.7mm species:
Indian silver bird, African silver mouth bird, red head bird, gem sparrow, etc.
3mm bird species:
colored canaries, ordinary red belly skull, brown tits, black canary, all kinds of organ birds
4.0mm birds:
colorful birds, Afacia birds, ten sisters, pearl birds, hibiscus birds,
4.0mm-4.5mm Bird species:
tiger parrot, Australia. Prairie parrot. Campanulaceae glory Burke's
4.5mm-5.5mm Bird species:
big head parrot, Pacific, horizontal spot, peony, cherry, Godi style, etc.

Notice:
Please check the size of the perch before making a purchase in case the item is not suitable for your pet birds.