Maxi: 88 mm, for big skimmers

For air driven protein skimmers

ab Aqua Medic wooden air stones are produced from lime wood with very fine pores. They have a low pressure resistance and create very fine, even bubbles. To keep the skimmer running at its optimum performance level, the bubbles have to be monitored regularly, and it is recommended that the air stone be changed every 6-8 weeks.