Coilover Help: What are these?

I've had very squeaky rear Bilstein PSS10 coilovers for a while and just now, I pulled the rear wheels off and had a look.

Upon removing the blue guillotine sleeve (pulling it down), I noticed these broken yellow foam sleeves.
The RHS has both broken, the LHS has just one broken.

Can anyone tell me if these come with the Bilstein PSS10 coilover kit or have they been added on by my installer (I purchased second hand)?

RHS






LHS


I put these sleeves back on and taped them together again.
After apply silicone spray to all my bushings and spring joins, etc, i took the car for a drive and my noise has pretty much gone away, comes back on the odd occasion.

I'm wondering if these broken sleeves are the cause of my noise?

I guess time will tell as the silicone will eventually wear off so i will see if the noise comes back.

Thanks guys, makes complete sense these are bump stops.
Also makes sense that they would be broken given the car used to sit lower and on some spirited drives, I've hit full bump at speed which would cause them to break.

Given they are bump stops, they certainly would not be the cause of my squeaking rear suspension which means it must have been the silicone application to everything which has stopped the squeaking.