These are one the best air stones out there that money can buy. They are weighted to sink naturally and can be taken apart if they ever were to clog - so they can be cleaned or the disks replaced. They also work great insidesponge filters. Instead of replacing a cheap ceramic air stone every 4-6 months as they get worse and worse for bubbles, install one of these once and nearly never worry about it again. Tighten or loosen the disks to change how big the bubbles are.
I love this air stone! It is easily cleaned by unscrewing the cap and rinsing the filters in aquarium water. The fish often play in the bubbles created by the air stones as well. And it doesn't disintegrate as some air stones do.
