Okay I received a response from Ted Lea. He says for the Vertex membrane diffuser, the membrane holder has a smaller orifice in it that other membrane diffuser holders do not have. It makes the Vertex diffusers unique. This is a specially designed "flow control" and adds psi back pressure. It was designed and added to each diffuser to allow equal air distribution on multiple head diffusers especially when the diffuser assembly is not sitting perfectly level on the pond bottom. Once again it proves that Vertex is an innovator and leader in the pond & lake aeration industry.
