White nylon plastic with a matte finish and slight grainy feel.
About this Product
Triangles and pentagons that snap together. This is the 3-sided piece.
Look here to get the OpenScad and STL files for yourself:
And the matching pentagonal piece is: http://www.shapeways.com/model/1113000
The snapping tolerances were tested on a Makerbot Replicator 2; I haven't tried it in any of the Shapeways materials.