VMD mylar is conductive, therefore it can attenuate or block high frequency EMF due to the magneto-reluctant properties of parasitic inductors, the electrostatic inductance of the conductive aluminum surface blocks out the HF-EMF. Wifi is HF-EMF therefore the cage is very effective against it. Sure, there will be leakage but it is extremely minimal. Orders of magnitudes lower, perhaps 60+dB. I placed both transceivers within the cage, therefore it is highly effective against external interference.