PTFE ring looks broken on Top Boss (top of inlet)
The PTFE ring that is mounted on the Top Boss of the OPTIC inlet has a slit. It looks like that the ring is broken, but this is normal and it is done for the production of the Top Boss part.
This ring has no gas sealing function for the inlet.
This Top Boss Clamp Nut does not need to be replaced under normal circumstances.
If for some reason you like to replace this ring, you need part;
2406-2012 OPTIC Inlet Top Boss Clamp Nut