I never understand why they 'improve' a system by making it worse.
The old Sirion had a cartridge which was easy to remove.
The new one is complicated and twice as expensive.

On mine the alloy filter container had fused to the body and took some removal as the chain filter remover kept slipping.
In the end I used duct tape to get a grip.

Anyway it is all done now but I am left with a plastic sort of valve with a 24mm plastic nut on the end.
What is that for and where does it go?
It was in the filter box and I could not find a place for it.