Kasco Robust-Aire RA6 System 6:6 diffuser assemblies 600' 3/8" tubing. Robust-Aireÿ diffusers are the most efficient on the market and create more water flow to aerate your pond. Diffusers are designed to provide a fine air bubble with the least amount of pressure. The base is made of durable plastic and an open port allows filling with gravel to settle. It has a raised design that keeps the diffusers performing at an optimal level above the pond bottom. A durable, bolted, strain relief attachment_ensures that the weighted tubing will not become detached during installation or maintenance.