What are these small pads between the string and frame at throat?

[gbp1287]

I was told by my stringer, that for natural gut on the mains, they use these little pads to help round out the strings, my question is, what the heck are these, and do they impact feel and performance in any way?

https://imgur.com/a/utud8xL

 

[Soundbyte]

They're "power pads", just bits of leather. Made popular back in the day by the likes of Sampras et al