Description Features: Due to the bubble counter, you can clearly know the volume of carbon-dioxide through the rising air bubbles from the bottom to regulate the carbon-dioxide supply for plants in the fish tank. Additionally, it features a non-return function to prevent the backflow when the pressure changes. It is made of tough material, so it is durable and reliable. A small thing will make your fish tank different. Small and compact,easy to install and replace. Specifications: Material: Copper Color: Silver Interface specification: Threaded interface: G1/8 thread Quick screw interface: 4mm, suitable for aquarium co2/oxygen tube 4/6mm air tube Type:Single Head/Double Head Package included:1pc x Bubble Counter Valve Note: 1. Due to the light and screen difference, the items color may be slightly different from the pictures. 2. Please allow 0.5-2 cm differences due to manual measurement.