Outlets and switches can emit strong electric and magnetic fields. Conventional shielding with mumetal is possible, but tricky because it’s hard to make it look good, plus you need access to be able to use the switch/outlet. Now you can simply replace your Switch Plate or Outlet Cover with these custom shielded ones. Magnetic field reduction is 30 to 60% up close to the surface, depending on wire configuration. For severe cases, you can stack a double layer to achieve even better reduction. Electric field reduction is typically 75%. Attractive polished chrome finish with a nice perimeter detail. Solid metal (shielding alloy) and durable. Includes mounting screw(s). Two sizes: oversize (3½x5½”) and super jumbo (5½x7½”) for maximum protection. Make sure you have enough room between outlet and nearby moldings for these larger than standard covers. Very economical!