They fit cars with the 288 mm Bosch front brake calipers:
Xantia V6 (all)
Xantia HDI 110 (all)
Xantia Activa TCT (after RP 8001)
XM V6 (from 1997)
XM 2.5 TD (after RP 7476)
These were never fitted at the factory, but were later available for fitment by dealers where customers complained of rattling on rough road surfaces.
You can read more about them here
I have been looking for a set of these for a few years, and not found any.
As I have 2 cars that need them, I am considering making some or having a small batch manufactured, do any owners of cars with these brakes have interest in buying a set?
I do not yet have a price, but do not expect it to exceed the Citroen list price, which was around £50 for a set of 2 (enough for one car).