Slipper pads
 

What pads are used in the slipper? Are they off another model?

I need some spares but would prefer to find some in the UK than ordering across the pond (until my next RCM order anyway :D).

The slipper pads are their own items - not from or for anything else. The Slipperential is a ground-up product and nearly everything is custom and specific to the unit itself.

What material are they made of?

Material is propietery (developed by Ferodo brake company). :)