They are made from resin and come pre-painted. Although I think a better description would be pre-washed. The one's I received are much lighter in colour and although they appear to just have had a light brown wash they do look ok.
Below are some more pictures with a PSC Panther and Battlefront U.S. 105mm cannon included to give you an idea of the scale of the walls in comparison to 15mm tanks and infantry.
Each of the straight wall sections is about 2.5" long so with the corners and gate sections you get about fifteen feet of walling which works out for me at about 90p a foot which I reckon is a pretty good deal.
So what do I think of them? I like them and I'm happy with the purchase. They're a good height and can be used straight out of the box and at 90p a foot I can't go wrong, 9/10.