The set contains a variety of pads of different thikcnesses and diameters to accommodate different sizes of cymbals. Nice quality material, seems like they would last for a long time.
I use them only on the underside of the cymbal, in place of the bottom felt.
Do they work? Yes, in my opinion they do. They don't deaden the cymbals, rather they tame those harsh highs which can be grating if using bright cymbals. I wouldn't bother using them live, but for recording or just playing by myself, I really like how they smooth out those highs and make the brash/grating cymbals less so.