Matala 12" Round Rubber Air Diffuser-Pond/Lake Aerator Supplies-Replacement disc This Matala 12" diameter membrane diffuser (AD12) 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 160 lpm. Diffuser has a 3/4" male thread inlet. The disc is very low maintenance, wash with water and bleach as needed.