100% stainless steel. Suitable for 2 to 4 people. Durable, health friendly, airtight and silicone seal. They can go to the freezer, dishwasher and oven (except the lid). it is forbidden to put them in the microwave and pour boiling liquid into them. 4 pieces : 2 x 14cm / 1.1 L. and 2 x 18 cm / 1.1 L.