Wonderful storage boxes in two different sizes. The lids are in PP plastic and easy to close. The small box holds 250 ml and the large 450 ml. Please complete with other products from this series. The snack boxes are made of RPET, which is an environmentally friendly and durable material. Rätt Start's products in RPET contribute to reduced waste and a lower carbon footprint. RPET is not microwave safe but can be washed in the machine.