Our Membrane air diffusers are manufactured using EPDM rubber, with rows of perpendicular perforations that prevent tearing. The Models 130-S and 130 diffusers are tubular with a minimum inside diameter of 2-1/2" and overall length of 12" for the Model 130-S and 24" for the Model 130. The diffusers rest in a galvanized frame that keeps it raised out of the sludge and mud floor. The frame also acts as an anchor to keep the diffuser weighed down and from moving. The diffusers are a fine bubble aerator that has all all the advantages of a higher oxygen transfer efficiency. The major advantages of this diffuser is its trouble fee operation with low maintenance and ease of installation. The units come standard with a check valve to prevent water from backing up into the air feeder line.