Fluval Air Diffuser, 2-Pack. Compatible with all aquarium air pumps, the Fluval Air Diffuser is easy to install, quiet to operate and offers adjustable flow for customized bubble control, making it an ideal alternative to traditional air stones. Easy to install, quickly connects to airline tubing Secure suction cup mount for versatile positioning Large easy-grip dial for simplified adjustment Turn dial clockwise to increase pressure and counter-clockwise to reduce pressure Provides effective water surface agitation for better oxygenation Dimensions: 1.25″ L x 1.25″ W x 2.25″ H / 3 x 3 x 5.5 cm