Each set includes one 1" Ozone Resistant Oblong Gray Diffuser Stone and one 1" Ozone Resistant Oblong White Diffuser Stone. (Note: tubing is not included with the stone set.) These stones are made for the 3688 model.
Our diffuser stones are made of crystal quartz glass and have a coarse texture. This allows the ozone gas to be expelled through the stone creating fine bubbles that spread the ozone evenly throughout the water. These stones are made exclusively for the MP-Series Multi-Purpose Ozone Generators.