Large Air Stone Cylinders: Size: 1.4" D x 11.9" L. Suitable for large aquariums, ponds, DWC systems and aquaculture farms. NOT fit for small aquariums or fish tanks. Medium Bubbles: The air stones are made of reliable rubber material with superb air permeability, which allows abundant dense and even bubbles to spout from the cylinder. An ideal way to fully aerate your water tanks. Steady Output: Jetting volume: 30 L/min; Recommended air pump power: > 20 W. Standard ID airline tubing: 3/16" or 3/8". Efficient bubblers for constant air diffusion, keeping your fish or roots growing healthily. Stable in Water: Each aquarium air stone weighs 20 oz and comes with 2 square holders at both ends to increase stability. It always lies stably in the water and won’t move easily when bubbling. Easy to Use: Soak the stone completely in water for more than 3 hours before use. Simply clean it by wiping its surface with a cloth instead of brushing it after use. Aquarium 12 Inch Air Stone Cylinder for Larger Pump Bubble Diffuser for Outdoor Pond Garden Circulation System and Large Fish Tank, 2 Pack