Chilled bento box with built-in gel pack
The freezy pack is supposed to keep your lunch cool and safe. The manufacturers recommend wrapping the box tightly in a thick cloth or insulated bag to keep the contents cool for a longer period. They also recommend freezing whole lid and gel pack assembled together on a flat surface in the freezer, to ensure that everything fits together after freezing. 500ml box, non-microwaveable, bought at Daiso for US$1.50. Assembled view here. Blog entry here.