Check the listing for details. Pond Air Diffuser Stainless Steel Weighted Hydroponic Aerator KoiPond Tri Ring. Condition: New. Listed at 114.99 USD. Stainless steel weighted Triple air ring for dynamic water movement. *we can have manufactured any custom size* Easy to maintain FDA Polyurethane tubing that delivers even micro bubbles and lasts. Replacement bubble tube, if ever needed, is super affordable over having to purchase a whole new stone or rubber membrane model air diffuser. The three rings in their different sizes together create a dynamic movement of water. The rings stay put on the pond bottom where placed. They require less pressure which helps your air pump life due to less demand and less back pressure. 14.5" outer ring 10" center ring 6 1/2" inner ring. Pond Aquarium Air Bubble Stone Fish Tank Hydroponics Aerator Tri Ring. Condition is New. Shipped with USPS Priority Package. Optimal air 60 liters to 1200 lpm. But works great on a 40lpm air pump! Excellent paired with economical Hakko air pumps.