Interestingly, the magnet itself is enclosed in metal (apparently steel), yet still affects the compass. I tried placing several different types of material between the compass and magnet: a cup of coffee, my leatherman wave knife, plastic safety glasses, a pad of paper. None of these materials seemed to have any effect on the magnet's ability to move the compass. In fact, the knife actually increased the distance from which the magnet would affect the compass. I could find no material that did not allow the magnetic force to pass through.