The must have balling accessory. These three vessels have been specifically designed for use in the balling method of supplementing a marine aquarium with Calcium Magnesium and Alkalinity with the use of a dosing pump. They each hold either 0.6 1.5 or 2.5litres of liquid and draw from the bottom. The pipes are the correct size so ordinary aquarium air line can be pushed on to provide a secure grip straight from your dosing pump (we recommend silicone airline). They give a professional look you don\'t get from plastic bottles and are very user friendly as the top just pulls off easily for topping up. The suction from the dosing pump doesn\'t allow any liquid to drip out when you remove the pipe complete with the lid. Perfect for people who are limited with space inside their cabinets. Each vessel can easily be completely dissembled for ease of maintenance and cleaning etc.