Includes air check valve to prevent water from filling airline when not in use.  Underlay board keeps diffusers from settling into the mud and prevents sediment erosion.  The membrane diffusers are manufactured using EPDM rubber, with rows of perpendicular perforations that are ideal for pond aeration. These diffusers are easy to clean. They do produce a slightly larger bubble than the air stones. The major advantages of this diffuser are its trouble free operation with low maintenance and ease of installation.  

• Four standard diffusers are 6" long and connection is for 1/2" ID tubing
•  Measures 24" x 24".
• Incredibly strong
• Recommended flow is  1.6 to 6.8