recipient of the design distinction award by ID Magazine, the opus incertum is made from expanded polypropylene and measures 39.4" x 13.8" x 39.4" and can be stacked. useful for a moderate amount of books or as a display shelf, a single unit has a capacity of 110 pounds. please note that this capacity stays the same when you stack the units- so the base can only support 110 pounds in total. can be used indoors or outdoors. 100% recyclable.