Leica E55 filters

I need to get a 85B filter for my Leica R. I believe my 50 and 35 Summicrons are both E55, is that a plain old 55mm diameter? I understand that some filter won't let the sliding hood extend (ok, not that bothered about that) but are some brands better than others when it comes to allowing the hood to move?

Thanks!

I'm using B+W filters (UV and pola). The sliding hood on my Summicron-R 50mm extends easily with the filter screwed in. Any filter should be fine.

Cool thanks.