These are - depending on material - used for different high gloss polishing finishes:
Cotton is suitable for polishing plastic resin, gold, titanium and steel. You can choose between texture, diameters and thicknesses.
Leather is ideal for a dry finishing polish, whereas cloth discs with pleats are employed for precious and non-precious metals. The pleats provide good cooling and service life as well as reduce fraying and ensure better paste adherence (also with pumice).