These are feetpads made out of a rubber material, not silicone. Good for people who are extra rough on their paws, since the rubber will stand up to more wear-and-tear than silicone will.
Feetpads are perfectly safe to use indoors and outdoors on concrete or grass, and they are nearly as strong as the soles of shoes, so keep in mind that just like soles, will eventually start to wear out if used on concrete for a very long time.
If you are making sockpaws, it's not advised to add these pawpads to them, unless the sockpaw has a solid base it's built on. Otherwise it ends up being too rough on your feet to walk right on the pads, since they are more solid.
IF YOU INTEND TO DANCE IN YOUR FEET, PUTTING PAWPADS ON THE BOTTOM OF YOUR FEET IS NOT ADVISED.THEY HAVE AN EXTREME AMOUNT OF GRIP AND YOU WILL LOSE THEM.