Small Air Stone Cylinders: Size: 1.15" D x 3.25" L; Weight: 3.88 oz. The small cylinders are well-constructed for continual bubbling. Ideal for small fish tanks, DWC systems or small ponds. Medium Bubbles: The air stones produce a good amount of dense bubbles. A great way to increase oxygen solubility in your aquariums and enliven the aquatic lives. Steady Output: Jetting volume: 4 L/min; Recommended pump power: > 2 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 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 1 hour before use. Clean it regularly with a brush as it gets clogged after weeks or months of usage. Aquarium 3 Inch Air Stone Cylinder for Air Pump Bubble Diffuser Release Tool for Fish Tanks, 2 Pack