I've been using these picks on and off for about 5 years now.  I'm not a very good player, and it shows in my lack of knowledge on picks.  Since these picks don't show what their thickness is I guessed and went with the mediums.  Well, they're definitely thinner than the .73mm Dunlop Tortex picks, which I've mostly been using.  I recently went back to this gel pick and found that rhythm sounds much better with these, and the grip is slightly better as well.  I didn't realize how much the material and thickness of a pick impacted my tone, especially on electric guitar.