Penn Plax AS4 Aqua Mist Air Stones 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 1 inch (or 2.5 centimeters) on each side. 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