Caliper slider kit

Hi guys. Just fitting brake caliper slider kit on my cabby.
Got them in bits and have noticed that there are white plastic type bushes that sit between the metal bush and the rubber sleeve.
New kit didnt come with these so are they required or has the design changed?
Any help appreciated.

Cheers.

Yes, and no.

I have seen this issue as well, and it was a dickens of a time to re-install them.

On one of my later rides, when I re-did the brakes these were missing.  I opted to use never-seize on the bolts that the sliders slid on as well as a thin coat on the sliders to keep the outsides of them to the rubber boots.

I have never had the issue with them when re-placing the pads again.

I can also remember one of my Cabbies that I had the slider part because fused (probably my rust) to the bolt.

But if you think on it the bolt holds the slider in position and the steel sleeve doesn't move at all, as it is the caliper that slides on it.

So yes, and no is my answer.  Yes originally, but no after if you never-seize.