This part is listed as a replacement filter for the EC9335M machine, but after asking DeLonghi, they told me I could also use it in my EC9355M, so I bought it.
I'm happy with it so far, except for the fact that I can't seem to be able to remove the detachable part in order to clean the inside.
Also, the filter seems just a tiny bit too small, which makes it kinda pop out the portafilter when you remove it from the machine after brewing your coffee. It doesn't seem to matter though. It still works fine and allows you not to care about the perfect settings like you have to when you use the unpressurized filter. For example, it's very useful if you have some coffee that wasn't ground using the usual settings on the machine and you fear you won't get enough pressure. This filter should make up for the lack of pressure and you won't waste precious coffee :)