It's a shame that the Fluval 404 is such an awesome filter.... I keep replacing these stupid impeller covers because the clips keep snapping and don't hold the impeller in place, causing a loss in water pressure and a horrible clicking noise...But the Fluval is so good that I keep buying these things by the dozen, and swapping them out when they break...It's definitely a design flaw. I have 3 of these on my 150g tank, and each one has had this part break several times in it's lifespan... Same break, same spot. Every time... The pressure becomes too great on the impeller, the clip weakens, and SNAP! the clip breaks...It's becoming harder and harder to find these pieces, and i'm terrified that i'm going to end up replacing my 404's when I can no longer find this part... That will be a sad day...