I've used their rock walls and like them a lot. Here is a cut on my layout using pink foam to build the mountain and their Rubber Rocks product for the rock facing of the cut. You simply cut what you need with a pair of scissors and glue it to the pink foam with foam compatible construction cement from your local building supply store. Fill in any gaps between the rock face and foam with Sculptamold and paint to suit. The whole mountain lifts out.
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Ken