This Thread Storage Unit comes with the three shelf unit, the shelf supports and mats, and the organizer base box that holds the three boxes neatly together. The file is compatible with both the 8x12 and 12x12 mats. The finished unit is approximately 6" x 9" x 1-1/2" with each shelf being just over 2" wide and 1-3/4" tall.
This box assembles similarly to the following:
Please see post links above for more details.