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.