The Ultra+Latch 3.5 Cup Rectangle food storage container features a domed locking lid with air-tight leak-proof silicone gasket seals, to keep food fresh longer. The Boy Blue color-coded matching system makes it easier to find the correct lid and base combination. Containers stack neatly in use and nest efficiently in storage. Ultra+Latch containers are freezer, microwave and dishwasher safe, as well as BPA-free and phthalate-free.