As of July 2015, Walmart.com sells two sizes each of Duck and Bankers Box brand heavy duty cardboard moving boxes. Both brands offer boxes that are 18 inches by 18 inches by 24 inches.
Duck boxes also come in 16 inches by 16 inches by 15 inches, and Bankers Box makes moving boxes that are 18 inches by 18 inches by 16 inches. Duck boxes are available individually or in a moving kit that includes both box sizes and other packing materials, such as tape and bubble wrap. Bankers Box moving boxes are available in packs of six or eight. All of the boxes fold flat for easy storage when not in use.