MAILING BOXES: The mailer boxes are made of kraft corrugated cardboard, lightweight but sturdy, which is great for mailing small items PACKAGING SUPPLIES: The shipping boxes are great for small business or for wrapping Gifts, especially decorating them with labels, stickers, ribbons EASY FOLD: The corrugated boxes are easy to put together in seconds, the tuck top has two locking taps to close boxes and keeps secure SMALL SIZE: The dimensions of the stackable cardboard boxes are 4x4x2 inches (LxWxH), and the internal dimensions are about 3.6x3.6x1.8 inches FLAT PACKING: 100-pack box mailers put in a carton, which is easy to ship and storage.