Recently i bought a bunch of Rollei round filters. Those filters are special in the regard that they are not classic screw filters, but magnetic filters you clip onto each other.

This does mean though, that you need a Base Ring which actually attaches to the lense by screwing. The filters themselfs do not have to have the same diameter as the lens though, for that purpose Rollei sells seperate Step up rings, which connect a smaller diameter size to a bigger one.

This gives the advantage that you only need the actual filters in one size and with the Step up rings can connect them with smaller lenses. For lenses which are already the correct size, you need a fitting “Base ring”.

The Big question i had was: If i buy the Step up ring, do i still need a classical Base ring on top for the actual filters.

Since the order was quite pricy i searched a lot but could not find a definite answer. I went ahead and betted that i do not need extra Base rings.

Which luckily turned out to be True, you do not need a Base ring with a Step up ring. The Step up ring also has a screw mechanism for the lense directly.

Disclaimer: The links are not affiliate links, i am just writing the blog post which i needed when i bought them.