20x20x15" Corrugated Boxes for Shipping, Packing, Moving Supplies, 20 Total | eBay
Amazon.com: BOX USA Moving Boxes, Extra Large 20" x 20" x 15" (12 Pack), Corrugated Cardboard Box for Packing Packaging Storage Mailing, and Shipping for Office of Home, 32 ECT - Pack
uBoxes Moving Boxes, Large 20 "x 20 "x 15" (Bundle of 12)Boxes For Moving - Sam's Club