Is 1900 ml big enough for a bag of flour?

A 1900 ml container holds roughly 1.7 to 1.9 kg of flour depending on how packed it is, so a standard 2 kg bag may not fit in one. Split it across two containers or leave headroom for scooping.

Are these containers really airtight?

The double lid is designed to press down and seal, which keeps dry goods fresh and pests out. Press the lid down evenly on all sides; a partly seated lid lets air in.

Can I put them in the dishwasher?

The plastic bodies and lids are generally hand-wash recommended to keep the seals tight and the plastic clear. Warm hand washing with mild soap is the safer routine.

Can I store liquids or sauces in them?

They are built for dry goods. Liquids can seep past the lid seal and the rectangular corners are hard to clean, so keep them for flour, rice, cereal, pasta and snacks.

Do the containers stack safely when full?

Yes, the flat rectangular tops are made to stack. Stack only same-size units and keep heavier containers at the bottom of the pile.

Will strong-smelling foods leave a smell in the plastic?

Plastic can absorb odors from spices, coffee or strong snacks over time. Air the containers out and keep very pungent items in their original packaging inside.