This bottle cap is very suitable to be DIY Co2 systems accessory that the size fits common. Please allow 1-3mm error due to manual measurement. The colors may have different as the difference display, please understand. The item "Aquarium Bottle Cap for Live Plants CO2 Diffuser Air Generator System Tool NEW c" is in sale since Thursday, January 18, 2018. This item is in the category "Pet Supplies\Fish & Aquarium\CO2 Equipment".9479" and is located in China. This item can be shipped worldwide.