Is the insulation bag of the insulated lunch box useful?

When buying lunch boxes, you need an insulating bag to enhance the thermal insulation effect.
Lunch bag - refers to the most convenient bag to carry. It usually refers to a bag that carries tableware and can hold lunch boxes, cups and water bottles. The main material of the product is high-density Oxford cloth, an environmentally friendly fabric with high density, strong cold retention, light weight, neither soft nor hard, and non-toxic. It is called an environmentally friendly material.