description of goods:Do you want to make your fish tank different? Our new designed carbon dioxide bubble counter is a good choice for you. Made of high quality material, which will be durable and reliable. With non-return function to prevent the backflow when the pressure changes. It can help you to see clearly the volume of carbon dioxide and supply the plants with enough carbon dioxide.Features: Made of high quality material, which will be durable and reliable. With non-return function to prevent the backflow when the pressure changes, and this can ensure the water plant table and CO2 bottle from damage. It can count the volume of carbon dioxide and supply the plants with enough carbon dioxide. East to install and use, a good choice to make your fish tank different. Double head and single head are available, you can choose according to your needs. Spec:Condition: 100% Brand NewItem Type: Bubble CounterMaterial: Aluminium Alloy & AcrylicColor: SilverOptional Type: Double Head, Single HeadDouble Head Size: Approx. 8.2 * 2cm / 3.2 * 0.8inch(L * D)Single Head Size: Approx. 8 * 2cm / 3.1 * 0.8inch(L * D)Package Weight: Approx. 32~34gInstall Method:Single Head Bubble Counter: 1. Take out the seal ring and install on the trachea interface of the valve, then tighten the bubble counter.2. Add 4/5 water in the bubble counter and then tighten the top cover. Plug the CO2 pipe and then tighten the trachea fastening nut.Double Head Bubble Counter:Add 4/5 water in the bubble counter and then tighten the top cover. Plug the CO2 pipe and then tighten the trachea fastening nut.Package Include:1 x Bubble Counter