Pondmaster Air Diffusers are made from flexible tubes and do a great job of evenly distributing bubbles inside a hydroponic reservoir. They also put less stress on air pumps, helping them last longer. Pondmaster Air Diffusers are made from flexible tubes and do a great job of evenly distributing bubbles inside a hydroponic reservoir. They also put less stress on air pumps, helping them last longer. 6\” STRAIGHT AIR DIFFUSER – ITEM# 14570 For Use with Pondmaster AP-20 and AP-40 Air Pumps 7\” DIAMETER RING AIR DIFFUSER – ITEM# 14580 For Use with Pondmaster AP-40, AP-60 and AP-100 Air Pumps AIR DIFFUSER KIT – ITEM# 14575 Includes 6\” Straight Diffuser and 20 Feet of 58\” Tubing to fit Pondmaster AP-20 and AP-40 Air Pumps.