The pads are made out of a sticky polyurethane substance that does not leave any residue. All you have to do is apply pressure to the pads in order for them to stick. They're pressure sensitive, so the more pressure you apply to the pads the better they will stick. The pads are so sticky you could literally throw your phone at them and your phone will stick. Even though they are sticky they are easily removable. Both pads are the same so they work the same when you're sticking them on tables, windshields, or your phone or tablet. Just apply pressure and they will stick.