how does this seal ? concealed shower valve

[Evren]

I am trying to fit a concealed shower valve into this wall but i have some doubts about the sealing around the control knobs when the whole thing comes together.

As per photos the decorative rings that go between the cover plate and the threaded piston things has internal rubber O ring which seals the gap between the piston and the ring. However the ring does not have an O ring on the outside even though there is a recess for it on the outer diameter which is I believe meant to seal between the ring and the hole in the cover plate.
Am I mean to buy some rings for the outer dia of the ring to create the seal or use silicone etc ?

I have access to the back of this wall if that makes any difference.

thanks all in advance for replies

 

[Deleted member 267285]

Does it mention anything in the instructions? Call technical helpline?

 

[Evren]

Does it mention anything in the instructions? Call technical helpline?

Chris its a 2nd hand unit which i thought i had all parts for but perhaps the inner O rings did not come with it.
Sadly there is no manufacturer info i can find either

 

[thomp1983]

You asked this same question just over a week ago, the answers still the same there's usually o rings for that groove.

You should he able to order some online cheap enough you'll just need to measure the diameter of the decorative ring.

The other option is a bead of clear silicone and fit them in place and leave to set