It was made of inflated rubber cells.
Eric "Winkle" Brown described it very well in his book "Wings on my Sleeve".
If I recall right the consensus was that with relativly light aircraft, "landing" relativly slow with low vertical speeds, the system was very effective. But unfortunatly the aircraft developed the other way - high landings speeds, high sink speeds, and heavy (or with pylons etc sticking out of the fuselage and under the wings).
The Americans tested the system too and had some hairraising experiences with it. I thing they used the Grumman Panthers and Cougars for testing. John Moore was heavily engaged in that project, see his book "The wrong stuff, flying on the edge of disaster".
Cheers,
Mark
