The oasis bird bottles have a specially designed "triple ball point" tip with a built in reservoir featuring a red nylon ball to attract birds. There are two stainless steel balls above the red ball to add weight and seal against dripping. The drinking tube-style oasis bird bottles offer a sanitary clean water supply that is not contaminated by seed, seed hulls or droppings. The green bottle color helps protects water supply from damage by sunlight, preserving vitamin and/or medication potency and inhibiting bacterial growth. The floating white ball indicates water level at a glance. The 4 ounce bird Bottle is intended for use by small birds such as parakeets (budgies), canaries, finches, Waxbills, most conures, lovebirds and parrotlets. This size is ideal for single birds, breeding cages, transport cages and small groups of birds. When used with colonies of birds or in flight cages, install several bottles to insure an adequate water supply.