uxcell Black Mineral Bubble Air Stone Diffuser for Aquarium Fish Tank Pond Pump Color: Black,Gray; Total Size: 135 mm / 5.3"; Material: Mineral, Plastic; Model: NAJ-301 Net Weight: 232g; Stone Size: 40 x 80 mm / 1.6" x 3.15" (D*H); Fits for 0.16"/4mm inner diameter tube. Increases oxygen and lowers CO2 levels. An important accessory to keep aquatic fish for respiration process. Create an abundant cascade of small to tiny bubbles rather than a limited number of larger bubbles. Suitable for aquarium, fish tank, pond hydroponic and circulation system. Soak it in water for at least 15 minutes before use.