Oasis Bird Bottles feature the Cherry-Red drinking tip (a lower red nylon ball that visually attracts birds and 2 stainless steel balls above that for weight.) This drinking tube-style offers a sanitary clean water supply that is not dirtied by seed seed hulls or droppings. The traditional green bottle color protects water supply from damage by sunlight thereby preserving vitamin and or medication potency and inhibiting bacterial growth. A floating white ball indicates water level at a glance. Each bottle serves between 1 to 4 birds depending on species & diet. 4 ounce size – usually used for canaries finches parakeets (budgies) and lovebirds.