Matala Rubber Membrane 9" Air Diffuser-Aerator-Stone-Round disc-epdm-Pond-Lake-Replacement This Matala 9" diameter membrane diffuser (AD9) is a great alternative to airstones in many aeration applications. It contains hundreds of "I" slots that open as air pressure builds inside of the diffuser- providing uniform bubble distribution. Capable of handling air flows of 25 lpm to 80 lpm. Diffuser has a 3/4" male thread inlet. The disc is very low maintenance only needs water and bleach to clean as needed.