Flexible, easy push-through bases; leak-proof hinged lids; The pots click together for easy filling Freeze, microwave & serve pop out frozen food by using really clever, soft push-through bases or thaw/defrost and serve directly from the pot he marker pen included enables you to write on the pot to make for easy detection of frozen food! They are BPA Free, Dishwasher and Microwave Safe and suitable from 4 months.