I just got my 303B yesterday and test it. Works perfect. I was going to replace my
C360 and send it back to save $70 but decided to put the 303B on the shelf as a spare now. If I knew about these filters before I bought the Marineland, I would have gotten it first.
Do you think you could pop out the impeller on the c360 and compare it to the 303b? If they are the same then sun sun pimps will have a source on replacement parts