(01/14/2010) - Few things live up to expectations, especially when it comes to equipment in this hobby. But this one really does make an incredible difference. I never really noticed my overflow making too much noise because my skimmer was drowning it all out. Well I upgraded to a quieter skimmer and now all I could hear was the gurgling noise from my HOB overflow. After putting in the silencer the noise just disappeared. Pretty neat invention. No instructions but it's pretty self explanatory. Now I need to figure out a way to quiet the sump! Maybe some filter socks.