These are made of super-thin 1/8" neoprene foam, like 1/3 the thickness of a cheap can cooler. They muffle maybe 20% of the volume. You could throw a towel over each drum and get at least the same amount of damping. You could probably buy a much thicker sheet of the same material and cut your own for the money.

real cheap and easy way to practice on your set instead of getting another pad set. Though the bass head muffler doesn't do much. Other than that, it's well worth it.