Material: Crafted from aluminum alloy and acrylic material, this CO2 bubble counter ensuring durability and style in your aquarium setup Easy Water Refill: The design allows for smooth and effortless water refilling by simply twisting open the top, ensuring easy maintenance Clear Viewing Window: Equipped with a visible window to monitor bubble speed at a glance, providing accurate control over CO2 levels in your aquarium Quick Connect Design: Experience the convenience of a quick connect system that allows for easy installation in just 3 seconds, making setup easier Check Valve Design: Features an intricate check valve system to prevent backflow of water, safeguarding your equipment from potential damage while offering double connection options with its included metal rod or soft tube for flexible installation choices Specification: Material: Aluminum Alloy, Acrylic Size Chart: Height: 8.6cm/3.39inch Hole Diameter: 0.6cm/0.24inch Package Includes: 1 Piece Double Head Aquarium CO2 Bubble Counter Note: Please allow slightly errors due to manual measurement and different monitors.