1 kg. Fast food plastic box is a kind of fast packaging for packaging food. The conventional size is 500ml, which can hold 500ml of water, that is, 500g of water, equivalent to 1 kg. Disposable snack boxes have changed from foamed lunch boxes to environmentally friendly lunch boxes. The original foam lunch box was eliminated because it was not resistant to high temperature and the production process caused damage to the environment. Instead, plastic lunch boxes and paper lunch boxes are used.