Penn Plax Aquarium Mist Sphere Air Stone, 7/8-Inch, Aqua STEADY FLOW OF BUBBLES: which will provide a better supply of oxygen to your fish, and a beautiful look to your aquarium. SMALL SIZED MIST AERATOR: measures at a 7/8 inch diameter (or 2.2 centimeters). SHOP PENN PLAX FOR ALL YOUR AQUARIUM NEEDS: Penn Plax sells a wide variety of Aquarium products; such as tanks, filters, decorations, and much more