Welcome to our store! [Essential Aquarium Accessories]: Maintaining an appropriate level of CO2 in your aquarium is one of the most important factors for the health of the ecosystem of the artificial aquarium. With the CO2 measuring aquarium tester, you can easily check the CO2 content of your aquarium at any time. Help your fish and plants grow healthy. [High Quality Material]: The aquarium CO2 tester is made of non-toxic, safe and durable transparent glass. Transparent colors help you see the water color change more clearly and understand the CO2 content. [Strong suction cup design]: The aquarium CO2 tester is suction cup designed . Easy to install and remove. Just install the product on the inner wall of the aquarium, within 5 - 10 cm from the horizontal, for long-term use. [Easy to check the CO2 content ]: The glass drop tester is very easy to use. It suffices to observe the color of the liquid to know the CO2 content. Green indicates good CO2, blue indicates lack of CO2, and yellow indicates excess CO2. [Convenient and simple]: The package includes 2 pieces of CO2 glass tester with a size of 5*5cm. It is lightweight and convenient for professional aquarists or beginners. There may be some size errors in the product you receive due to hand measurement The product you receive may be slightly different from the picture due to different monitors Thank you for meeting me, hope I can help you. Good life Actual quantity shipped: 2 piece(s) 100% satisfaction - Our customers are our priority. If you find any problems with the products after receiving the goods, such as damage and incorrect quantity, please contact us immediately. We do our best to provide you with satisfactory after-sales service