Description: Aluminium Aquarium Inline CO2 Bubble Counter with build in check valve. When the regulator is open,to calculate your CO2 rate by counting how many bubbles pass through the counter , with the piece of mind that your equipment is protected in the event of water siphoning back towards your equipment. A must have for with CO2 , a bubble counter allows the user to the CO2 rate by counting how many bubbles pass through the counter check valve prevents water from your aquarium from siphoning back into fragile and expensive CO2 equipment such as regulators and solenoids. Easy to read and easy to maintain. Designed in a typical bubble counter shape, this clear aluminium bubble counter,perfect to get an accurate bubble count without the need of bulky and expensive equipment. To use, simply unscrew one end and fill the bubble counter with water, Specification: Material: Aluminum Alloy + Glass Length: Approx. 8cm/3.15inch 2 head is suitable for 4mmx6mm tube Package Includes: 1 Piece CO2 Bubble Counter