I started modifying a couple of sponge filters so I could use a no clog stone in them. The bubble output is great and the fact that you can add or remove the individual sections is an added bonus.
Excellent, the best
Still working 8 months later with no issues.
I use these in all of my betta tanks and love them. I was getting frustrated with having to replace ceramic airstones but since making the switch the airflow has been constant and maintence free.
This is the second bunch I purchased because the first set was so awesome. These are so much better than the ceramic ones.