Settings > Delivery Settings > Containers (/admin/containertypes) manages the container types (trays, jars, cups…) that go inside bags or that meals are packed in. The list has Active and Inactive tabs, each with ID, Name, Type, Slot Size, Used By (how many bag types reference it) and an Edit button. Containers are assigned to bag types (for packing lists) and to meals (to work out how much bag space a meal takes).