How to seal off a closed receptacle?

The adjustable receptacle has a dimension width of 22mm

To make it sealed at the sides you need 1mm extra on both sides, so 24mm

However the tolerance on manufacturing the gummi is +/- 0.5mm on both sides, which means if we manufacture a seal of 24mm, then you can get into the situation that the seal has a dimension of 25mm

So: we would need 25mm

If you want to seal off the current receptacle, it makes no sense, as it is open???

You’ll need to transition to the closed receptacle.

My advise is not to use anymore the narrow type.

As the drawing that you show is wrong,

You see that the countersunk already starts at sides, which means, no material to seal off

So you need 18mm

However, again, the distance is narrow.

So you need to add 1mm on both sides: which is 20mm to seal it off

So with the tolerances of +/- 0.5mm

We would need 21mm instead of the 18

The recommended thickness of the seal = 1mm, still need to request then what the compressed thickness is.