White nylon plastic with a matte finish and slight grainy feel.
About this Product
Triangles and pentagons that snap together. This is the 5-sided piece.
Look here to get the OpenScad and STL files for yourself:
And the matching triangular piece is: http://www.shapeways.com/model/1112999
The snapping tolerances were tested on a Makerbot Replicator 2; I haven't tried it in any of the Shapeways materials.