This is a Toy brick compatible with the industry standard (like Lego, Mega Blocks etc.).
Flat version (= 3.2mm - 1/3 of the standard block).
4 by 4 knobs wide (32mm).
Nothing special about this - it has the same form as the piece you could buy in toy store (except of course for the great choice of materials here at Shapeways).
If you are interested in special "Lego compatible" pieces that are not otherwise available, please tell me.