Anyone seen this stuff? I'm impressed with the idea, as I know 3rd party speakers in the MK4 are going to get wet/damp because the OEM speakers were mounted in a special plastic surround 'thing' but the Autoloeads mounting adapter (et-al) do mean my old speakers got very corroded and it probably explains the little bit of water I sometimes get along the sill inside the car.
Skinz Moisture Guard seems to be nothing more than a slightly stretch, thin polyurethane (spelling?) foam which you put between the speaker mount/speaker and the door - it seals the speaker to stop water getting to it and reputes to offer some sound deadening too. Can this type of thing be bought in a different guise from a fabric shop or similar?